Conjugates of quaternized tubulysin compounds

ABSTRACT

Compounds and compositions are disclosed in which a quaternized drug unit is linked to a targeting ligand unit from which a tertiary amine-containing drug is released at the targeted site of action. Methods for treating diseases characterized by the targeted abnormal cells, such as cancer or an autoimmune disease using the compounds and compositions of the invention are also disclosed.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims benefit of priority to U.S. Appl. Ser. No.62/263,578, filed Dec. 4, 2015, U.S. Appl. Ser. No. 62/263,587, filedDec. 4, 2015. U.S. Appl. Ser. No. 62/309,448, filed Mar. 16, 2016, andU.S. Appl. Ser. No. 62/309,462, filed Mar. 17, 2016, all of which areincorporated by reference herein in their entireties.

BACKGROUND OF THE INVENTION

The invention relates to ligand-drug conjugates (LDCs) for targeteddelivery of tubulysin compounds to abnormal cells associated with agiven disease state or to the vicinity of such cells. The targetingligand of such an LDC selectively exposes abnormal cells, in contrast tonormal cells distant from the abnormal cells, to the tubulysin compound.That selective exposure is accomplished by concentrating the compound atthe desired site of action as a result binding of the targeting ligandof the LDC on, or in the vicinity of, the abnormal cells. As a result,exposure of distant normal cells to the tubulysin compound is reduced,thus reducing undesired side effects due to the cytotoxicity of thetubulysin compound while reducing the contribution of abnormal cells tothe disease state as a result of that cytotoxicity.

In general, the design of an LDC involves consideration of a variety offactors including the requirement that the drug has a site forattachment to a linker moiety that joins the drug to the targetingligand and is capable of releasing the drug at the target site. In oneapproach, tubulysin compounds have previously been incorporated intoLDCs through covalent attachment of a linker moiety to the C-terminalcomponent of a tubulysin compound, which usually is tubuphenylalanine(Tup) or tubutyrosine (Tut), either through its carboxylic acid moietythat has been transformed to a hydrazide functional group or through theC-terminal component's phenyl moiety through an amino substituentintroduced into that moiety. In another approach, attachment of a linkermoiety is to the N-terminal component, which in naturally-occurringtubulysins is D-N-methylpipecolic acid (D-Mep), after removal of itsmethyl substituent. In both approaches a modified tubulysin compound isreleased with a significant loss of cytotoxicity in comparison to theparent compound, which reduces its effectiveness as a therapeuticcompound.

Because of the difficulty in incorporating a tubulysin compound into aLDC that will conditionally release that compound in unaltered form soas to retain its cytotoxic activity, there is a need in the art for suchconjugates that use the tertiary amine nitrogen of a tubulysin'sN-terminal component as the site of conjugation in order for release offully active tubulysin compound at the targeted site of action. There isalso a need to mask the hydrophobicity of a hydrophobic tubulysincompound within a LDC to allow for increased loading of the compound tothe LDC's targeting Ligand Unit so as to increase the amount oftubulysin compound delivered to the desired site of action whilediminishing aggregation resulting in elimination of the LDC and torectify the loss of the acetate moiety in the tubuvaline (Tuv) componentin vivo. Either event alone or in combination diminishes the efficacy ofthe administered LDC.

SUMMARY OF THE INVENTION

Principle embodiments of the invention are Ligand Drug Conjugate (LDC)compositions, wherein a LDC composition is represented by the structureof Formula 1A

wherein L is a Ligand Unit (L); L_(B) is a Ligand Covalent Binding Unit;L_(P) is a Parallel Connector Unit; PEG is a Polyethylene Glycol Unit;subscript a is 0 or 1; subscript b is 0 or 1; A is a first optionalStretcher Unit so that subscript a is 0 when A is absent or A is presentso that subscript a is 1 and is optionally comprised of two, three orfour independently selected subunits (A₁, A₂, A₃, A₄); B is an BranchingUnit or a second optional Stretcher Unit (A_(O)) so that subscript b is0 when B is absent or B is present so that subscript b is 1 and isoptionally comprised of two, three or four subunits independently of A;subscript n is 1, 2, 3 or 4, provided that subscript b is 1 and B is aBranching when subscript n is 2, 3 or 4 and subscript b is 0 or 1 sothat B is A_(O) when subscript b is 1 and subscript n is 1; Su is acarbohydrate moiety; —O′— represents an oxygen atom of an O-glycosidicbond cleavable by a glycosidase; -J′- represents a heteroatom,optionally substituted when nitrogen; V, Z¹, Z² and Z³ are ═N— or═C(R²⁴)—, wherein R²⁴ is hydrogen, or alkyl, alkenyl or alkynyl,optionally substituted, or halogen, —NO₂, —CN or other electronwithdrawing group, or —OCH₃ or other an electron donating group, —O′-Su,or —C(R⁸)(R⁹)-D⁺, wherein at least two of V, Z¹, Z² and Z³ are ═C(R²⁴)—,provided, one any only one R³⁴ is —C(R⁸)(R⁹)-D⁺ so that —C(R⁸)(R⁹)-D⁺ isbonded to one of V, Z¹, Z², Z³ when that variable group is ═C(R²⁴)— andone and only one other R²⁴ is —O′-Su so that —O′-Su is bonded to anotherone of V, Z¹, Z², Z³ when that variable group is ═C(R²⁴)—, and the—O′-Su and —C(R⁸)(R⁹)-D⁺ substituents are ortho or para to each other;R⁸ and R⁹ independently are hydrogen, alkyl, alkenyl or alkynyl,optionally substituted, or aryl or heteroaryl, optionally substituted;R′ is hydrogen or is halogen, —NO₂, —CN or other electron withdrawinggroup; D⁺ is a quaternized tubulysin Drug Unit; subscript p is a numberranging from 1 to 24; and wherein said glycosidase cleavage initiatesrelease of a tubulysin therapeutic compound (D) from a Ligand DrugConjugate compound of the composition.

In some aspects, the Ligand Unit is that of an antibody, therebydefining an antibody drug conjugate (ADC) having an antibody LigandUnit, and the targeted moiety to which the antibody Ligand Unit iscapable of binding is an cell-surface antigen of targeted abnormal cellsthat is capable of cellular internalization of bound ADC.

Other principle embodiments of the invention provide for Drug Linkercompounds having the structure of Formula IA:

wherein L_(B)′ is a Ligand Covalent Binding Unit precursor and theremaining variable groups are as defined for Formula 1A.

In other principle embodiments the invention provide for Ligand DrugConjugate compositions and Drug Linker compounds having the structuresof Formula IB and Formula IB, respectively:

wherein V, Z¹, Z² and Z³ are ═N— or ═C(R⁴)—, wherein R²⁴ is hydrogen oralkyl, alkenyl or alkynyl, optionally substituted, or halogen, —NO₂, —CNor other electron withdrawing group, or —OCH₃ or other an electrondonating group, or —C(R⁸)(R⁹)-D⁺, wherein at least one of V, Z¹, and Z³is ═C(R²⁴)—, provided that one any only one R²⁴ is —C(R⁸)(R⁹)-D⁺ so that—C(R⁸)(R⁹)-D⁺ is bonded to one of V, Z¹, and Z³ when that variable groupis ═C(R²⁴)—, J represents a heteroatom, optionally substituted whennitrogen; R′ is hydrogen or —OCH₃ or other electron donating group, W isa peptide comprised of an amino acid sequence covalently attached to Jthrough an amide bond wherein that amide bond is cleavable by a proteaseand the other variable groups are as defined for Formula 1A and FormulaIB; and wherein said protease cleavage initiates release of a tubulysintherapeutic compound (D) from a Ligand Drug Conjugate compound of thecomposition.

In some aspects, the invention provides for LDC conjugate compositionsprepared from contacting a Formula IA compound or Formula IB compoundwith a targeting moiety having a reactive sulfhydryl, amino or aldehydemoiety under suitable conditions to effect condensation of the reactivemoiety with the L_(B)′ moiety of the Formula I compound, wherein L_(B)′is converted to L_(B) covalently bonded to a Ligand Unit thatcorresponds to or incorporates the targeting agent as a result of saidcontact.

In some aspects, L_(B)′ has the structure of one of:

wherein R is hydrogen or C₁-C₆ optionally substituted alkyl; R′ ishydrogen or halogen or R and R′ are independently selected halogen; T is—Cl, —Br, —I, —O-mesyl or —O— tosyl or other sulfonate leaving group; Uis —F, —Cl, —Br, —I, —O—N-succinimide, —O-(4-nitrophenyl),—O-pentafluorophenyl, —O-tetrafluorophenyl or —O—C(═O)—OR⁵⁷; X² is C₁₋₁₀alkylene, C₃-C₈-carbocycle, —O—(C₁-C₆ alkyl), -arylene-, C₁-C₁₀alkylene-arylene, -arylene-C₁-C₁₀ alkylene, —C₁-C₁₀alkylene-(C₃-C₆-carbocycle)-, —(C₃-C₈ carbocycle)-C₁-C₁₀ alkylene-,C₃-C₈-heterocycle, —C₁-C₁₀ alkylene-(C₃-C₈ heterocyclo)-,—C₃-C₈-heterocyclo)-C₁-C₁₀ alkylene, —(CH₂CH₂O)_(u), or—CH₂CH₂O)_(u)—CH₂—, wherein u is an integer ranging from 1 to 10 and R⁵⁷is C₁-C₆ alkyl or aryl.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1. Mean tumor volume (mm³) versus time (days) post-implantsubsequent to treatment of CD30⁺ L540cy Hodgkin lymphoma xenograft withDAR 4 quaternary amine-linked tubulysin antibody-drug conjugates havingquaternized Tubulysin M Drug Units linked via a val-ala dipeptide(cAC10-15) protease-cleavable unit in comparison to conjugation via aβ-glucuronidase-cleavable glucuronide unit (cAC10-82), and comparison ofantibody-drug conjugates having quaternized Tubulysin M (cAC10-82) andtubulysin ethyl ether (cAC10-57) Drug Units both linked throughβ-glucuronide-cleavable glucuronide linkers, all of have non-PEGylatedLinker Units.

FIG. 2. Mean tumor volume (mm³) versus time (days) post-implantsubsequent to treatment with DAR 8 glucuronide quaternary amine-linkedtubulysin antibody-drug conjugates containing quaternized tubulysinethyl ether Drug Units with (cAC10-66) or without (cAC10-57) PEGylationof their Linker Units, and quaternized tubulysin propyl ether Drug Unitswith (cAC10-67) and without (cAC10-58) PEGylation of their Linker Units.

FIG. 3. Mean tumor volume (mm³) versus time (days) post-implantsubsequent to treatment of CD30⁺ L540cy Hodgkin lymphoma xenograft witha DAR 8 glucuronide quaternary amine-linked Tubulysin M antibody-drugconjugate (cAC10-99) with PEGylation of its Linker Unit.

FIG. 4. Mean tumor volume (mm³) versus time (days) post-implantsubsequent to treatment of a xenograft comprised of a mixed populationof CD30⁺ Karpas and CD30-negative KarpasBVR tumor cells to assessbystander activity, wherein mice being the xenograft tumor were treatedwith a 0.5 mg/Kg single dose of glucuronide quaternary amine-linkedtubulysins antibody-drug conjugates in which the quaternized Drug Unitis that of Tubulysin M (cAC10-99), tubulysin ethyl ether (cAC10-66), ortubulysin methyl-(propen-2-yl) ether (cAC10-185).

FIG. 5. Pharmacokinetic profiles, shown as amount of total antibody(μg/mL) vs. time (days), of antibody-drug conjugates dosed i.v. in ratsat 1 mg/Kg having DAR 4 or 8 of quaternized Tubulysin M conjugated tohumanized IgG through a protease-cleavable val-ala (hIgG-15) or val-glu(hIgG-91) dipeptide quaternary amine linker without or with (hIgG-95)Linker Unit PEGylation in comparison to a β-glucuronidase-cleavableglucuronide antibody-drug conjugate of quaternized Tubulysin M (hIgG-82)having DAR of 4 without Linker Unit PEGylation.

FIG. 6. Pharmacokinetic profiles, shown as amount of total antibody(μg/mL) vs. time (days), of antibody-drug conjugates dosed i.v. in ratsat 1 mg/Kg with DAR 8 loading on humanized IgG antibody with glucuronidequaternary amine-linked tubulysin propyl ether with (hIgG-67) andwithout (hIgG-58) Linker Unit PEGylation.

FIG. 7. Pharmacokinetic profiles, shown as amount of total antibody(μg/mL) vs. time (days), of antibody-drug conjugates dosed i.v. in ratsat 1 mg/Kg with DAR 8 substitution on humanized IgG antibody withglucuronide quaternary amine-linked Tubulysin M (hIgG-99) and tubulysinethyl ether (hIgG-66) both with Linker Unit PEGylated.

FIG. 8. Mean tumor volume (mm³) versus time (days) post-implantsubsequent to treatment of CD30⁺ L540cy Hodgkin lymphoma xenograft dosedi.p. with 0.15 mg/Kg or 0.3 mg/Kg glucuronide quaternary amine-linkedTubulysin M antibody-drug conjugate with (cAC10-99) or without(cAC10-82) PEGylation of the linker having DAR of 8 and 4, respectively,or treatment with glucuronide quaternary amine-linked tubulysin ethylether antibody drug conjugate with (cAC10-66) or without (cAC10-57)Linker Unit PEGylation having DAR of 8 and 4, respectively, incomparison to treatment by i.p. dosing at 0.3 mg/Kg with DAR 4quaternary amine-linked Tubulysin M antibody-drug conjugate linked viaprotease-cleavable val-ala dipeptide (cAC10-15) without Linker UnitPEGylation.

FIG. 9. Mean tumor volume (mm³) versus time (days) post-implantsubsequent to treatment of drug resistant CD70⁺ 786-O Renal CellCarcinoma xenograft (MDR+) dosed i.p. with 0.5 mg/Kg or 1.5 mg/KgPEGylated glucuronide quaternary amine-linked tubulysin ethyl etherantibody drug conjugate (h1F6-66) or PEGylated glucuronide quaternaryamine-linked tubulysin methyl-(propen-2-yl) ether (hF16-185) both havingDAR of 8 in comparison to treatment with PEGylated glucuronidequaternary amine-linked tubulysin M antibody-drug conjugate (h1F6-99)having DAR of 8.

FIG. 10. Mean tumor volume (mm³) versus time (days) post-implantsubsequent to treatment of CD30⁺ cAC10-mc-val-cit-MMAE drug-resistantAnaplastic Large Cell Lymphoma xenograft (DELBVR ALCL) with DAR 4non-PEGylated glucuronide quaternary amine-linked tubulysin ethyl etherantibody drug conjugate (cAC10-57) or non-PEGylated glucuronidequaternary amine-linked tubulysin M in comparison to their correspondingDAR 8 PEGylated Conjugates (cAC10-66 and cAC10-99) dosed i.p at 0.3mg/Kg or 1 mg/Kg and to DAR 4 quaternary amine-linked Tubulysin Mantibody-drug conjugate linked via protease-cleavable Val-Ala dipeptidewithout Linker Unit PEGylation (cAC10-15) dosed i.p. at 1 mg/Kg.

DETAILED DESCRIPTION OF THE INVENTION Definitions

As used herein and unless otherwise stated or implied by context, termsthat are used herein have the meanings defined below. Unless otherwisecontraindicated or implied, e.g., by including mutually exclusiveelements or options, in these definitions and throughout thisspecification, the terms “a” and “an” mean one or more and the term “or”means and/or where permitted by context. Thus, as used in thespecification and the appended claims, the singular forms “a,” “an” and“the” include plural referents unless the context clearly dictatesotherwise.

At various locations in the present disclosure, e.g., in any disclosedembodiments or in the claims, reference is made to compounds,compositions, or methods that “comprise” one or more specifiedcomponents, elements or steps. Invention embodiments also specificallyinclude those compounds, compositions, compositions or methods that areor that consist of or that consist essentially of those specifiedcomponents, elements or steps. The term “comprised of” is usedinterchangeably with the term “comprising” and are stated as equivalentterms. For example, disclosed compositions, devices, articles ofmanufacture or methods that “comprise” a component or step are open andthey include or read on those compositions or methods plus an additionalcomponent(s) or step(s). However, those terms do not encompass unrecitedelements that would destroy the functionality of the disclosedcompositions, devices, articles of manufacture or methods for itsintended purpose. Similarly, disclosed compositions, devices, articlesof manufacture or methods that “consist of” a component or step areclosed and they would not include or read on those compositions ormethods having appreciable amounts of an additional component(s) or anadditional step(s). Furthermore, use of the term “including”, as well asother forms, such as “include”, “includes,” and “included”, is notlimiting. Finally, the term “consisting essentially of” admits for theinclusion of unrecited elements that have no material effect on thefunctionality of the disclosed compositions, devices, articles ofmanufacture or methods for its intended purpose and is further definedherein. The section headings used herein are for organizational purposesonly and are not to be construed as limiting the subject matterdescribed therein. Unless otherwise indicated, conventional methods ofmass spectroscopy, NMR, HPLC, protein chemistry, biochemistry,recombinant DNA techniques and pharmacology are employed.

“About” as used herein when used in connection with a numeric value orrange of values provided to describe a particular property of a compoundor composition indicate that the value or range of values may deviate toan extent deemed reasonable to one of ordinary skill in the art whilestill describing the particular property. Reasonable deviations includethose that are within the accuracy or precision of the instrument(s)used in measuring, determining or deriving the particular property.Specifically, the term “about” when used in this context, indicate thatthe numeric value or range of values may vary by 10%, 9%, 8%, 7%, 6%,5%, 4%, 3%, 2%, 1%, 0.9%, 0.8%, 0.7%, 0.6%, 0.5%, 0.4%, 0.3%, 0.2%, 0.1%or 0.01% of the recited value or range of values, typically by 10% to0.5%, more typically by 5% to 1%, while still describing the particularproperty.

“Essentially retains”, “essentially retaining and like terms as usedherein refers to a property, characteristic or activity of a compound orcomposition or moiety thereof that has not detectably changed or iswithin experimental error of determination of that same activity,characteristic or property of another compound or composition or moietyfrom which it was derived.

“Negligibly” or “negligible” as used herein is an amount of an impuritybelow the level of quantification by HPLC analysis and if presentrepresents from about 0.5% to about 0.1 w/w % of the composition that itcontaminates. Depending on context those terms may also mean that nostatistically significant difference is observed between measured valuesor outcomes or within experimental error of the instrumentation used toobtain those values. Negligible differences in values of a parameterdetermined experimentally do not imply that an impurity characterized bythat parameter is present in negligible amount.

“Substantially retains” as used herein refers to a measured value of aphysical property of a compound or composition or moiety thereof that isstatistically different of the determination of that same physicalproperty of another compound or composition or moiety from which it wasderived, but which such difference does not translate it a statisticallysignificant difference in biological activity in a suitable biologicaltest system for evaluating that activity (i.e., biological activity isessentially retained) or which has no biological consequence. Thus thephrase “substantially retains” is made in reference to the effect that aphysical property of a compound or composition has on a biologicalactivity that is explicitly associated with that property.

“Predominately containing”, “predominately having” and like terms refersto the major component of a mixture. When the mixture is of twocomponents, then the major component represents more than 50% by weightof the mixture. With a mixture of three or more components thepredominant component is the one present in greatest amount in themixture and may or may not represent a majority of the mass of themixture.

The term “electron-withdrawing group” as the term is used herein refersto a functional group or electronegative atom that draws electrondensity away from an atom to which it is bonded either inductivelyand/or through resonance, whichever is more dominant (i.e., a functionalgroup or atom may be electron donating through resonance but may overallbe electron withdrawing inductively), and tends to stabilize anions orelectron rich moieties. The electron withdrawing effect is typicallytransmitted inductively, albeit in attenuated form, to other atomsattached to the bonded atom that has been made electron deficient by theelectron withdrawing group (EWG) thus affecting the electrophilicity ofa more remote reactive center. Exemplary electron withdrawing groupsinclude, but are not limited to —C(═O), —CN, —NO₂, —CX₃, —X, —C(═O)OR′,—C(═O)NH₂, —C(═O)N(R′)R^(op), —C(═O)R′, —C(═O)X, —S(═O)₂R^(op),—S(═O)₂OR′, —SO₃H₂, —S(═O)₂NH₂, —S(═O)₂N(R′)R^(op), —PO₃H₂,—P(═O)(OR′)(OR^(op))₂, —NO, —NH₂, —NH(R′)(R^(op)), —N(R^(op))₃ ⁺, andsalts thereof, wherein X is —F, —Br, —Cl, or —I, and R^(op) is, at eachoccurrence, independently selected from a group previously described foroptional substituents and is sometimes selected from the groupconsisting of C₁-C₆ alkyl and phenyl and R′ is selected from a grouppreviously described for optional substituents and is sometimes a C₁-C₆alkyl. Exemplary EWGs can also include aryl groups (e.g., phenyl)depending on substitution and certain heteroaryl groups (e.g.,pyridine). Thus, the term “electron withdrawing group” also includesaryls or heteroaryls that are further substituted with electronwithdrawing groups. Typically, electron withdrawing groups are —C(═O),—CN, —NO₂, —CX₃, and —X, wherein X is halogen. Depending on theirsubstituents, an unsaturated alkyl moiety may also be an electronwithdrawing group.

The term “electron donating group” refers to a functional group orelectropositive atom that increases electron density of an atom to whichit is bonded either inductively and/or through resonance, whichever ismore dominant (i.e., a functional group or atom may be electronwithdrawing inductively but may overall be electron donating throughresonance), and tends to stabilize cations or electron poor systems. Theelectron donating effect is typically transmitted through resonance toother atoms attached to the bonded atom that has been made electron richby the electron donating group (EDG) thus affecting the nucleophilicityof a more remote reactive center. Exemplary electron donating groupsinclude, but are not limited to, —OH, —OR′, —NH₂, —NHR′ and N(R′)₂,wherein each R′ is an independently selected alkyl, typically C₁-C₆alkyl. Depending on their substituents, an aryl, heteroaryl orunsaturated alkyl moiety may also be an electron donating group.

“Moiety” as used herein means a specified segment, fragment orfunctional group of a molecule or compound. Chemical moieties aresometimes indicated as chemical entities that are embedded in orappended (i.e., a substituent or variable group) to a molecule, compoundor chemical formula.

For any substituent group or moiety described herein by a given range ofcarbon atoms, the designated range means that any individual number ofcarbon atoms is described. Thus, reference to, e.g., “optionallysubstituted C₁-C₄ alkyl”, “optionally substituted alkenyl C₂-C₆alkenyl”, “optionally substituted C₃-C₈ heterocycle” specifically meansthat a 1, 2, 3 or 4 carbon optionally substituted alkyl moiety asdefined herein is present, or a 2, 3, 4, 5 or 6 carbon alkenyl, a 3, 4,5, 6, 7 or 8 membered heterocycle or a 3, 4, 5, 6, 7 or 8 carbonoptionally substituted alkenyl moiety as defined herein is present. Allsuch numerical designations are expressly intended to disclose all ofthe individual carbon atom groups; and thus “optionally substitutedC₁-C₄ alkyl” includes, methyl, ethyl, 3 carbon alkyls, and 4 carbonalkyls, including all of their positional isomers, whether substitutedor unsubstituted. Thus, when an alkyl moiety is substituted, thenumerical designations refer to an unsubstituted base moiety and are notintended to include carbon atoms that may be present in the substituentsof that base moiety. For esters, carbonates, carbamates and ureas asdefined herein that are identified by a given range of carbon atoms, thedesignated range includes the carbonyl carbon of the respectivefunctional group. Thus, an C₁ ester refers to a formate ester, a C₂ester refers to an acetate ester and an unsubstituted C₁ urea refers toNH₂(C═O)NH₂.

The organic substituents, moieties and groups described herein, and forother any other moieties described herein, usually will exclude unstablemoieties except where such unstable moieties are transient species thatone can use to make a compound with sufficient chemical stability forthe one or more of the uses described herein. Substituents, moieties orgroups by operation of the definitions provided herein that results inthose having a pentavalent carbon are specifically excluded.

“Alkyl” as used herein by itself or as part of another term refers tomethyl or a collection of carbon atoms, wherein one or more of thecarbon atoms is saturated (i.e., is comprised of one or more sp³carbons) that are covalently linked together in normal, secondary,tertiary or cyclic arrangements, i.e., in a linear, branched, cyclicarrangement or some combination thereof. When the contiguous saturatedcarbon atoms are in a cyclic arrangement such alkyl moieties aresometimes referred to as cycloalkyl as defined herein. Saturated alkylsubstituents contain saturated carbon atoms (i.e., sp³ carbons) and noaromatic, sp² or sp carbon atoms (i.e., is not substituted withunsaturated, aromatic and heteroaromatic moieties). Unsaturated alkylsubstituents are alkyl moieties or groups that contain moieties asdescribed herein for alkenyl, alkynyl, aryl and heteroaryl moieties.

Thus, unless otherwise indicated, the term “alkyl” will indicate asaturated non-cyclic hydrocarbon radical, optionally substituted withone or more cycloalkyl or unsaturated, aromatic or heteroaromaticmoieties or some combination thereof, wherein the saturated hydrocarbonradical has the indicated number of covalently linked saturated carbonatoms (e.g., “C₁-C₆ alkyl” or “C₁-C₆ alkyl” means an alkyl moiety orgroup containing 1, 2, 3, 4, 5 or 6 contiguous non-cyclic saturatedcarbon atoms and “C₁-C₈ alkyl” refers to an alkyl moiety or group having1, 2, 3, 4, 5, 6, 7 or 8 contiguous saturated non-cyclic carbon atoms).The number of saturated carbon atoms in an alkyl moiety or group canvary and typically is 1-50, 1-30 or 1-20, and more typically is 1-8 or1-6. Typically, alkyl will refer to a saturated C₁-C₈ alkyl moiety, ormore typically is a C₁-C₆ or C₁-C₄ alkyl moiety with the lattersometimes referred to as lower alkyl. When the number of carbon atoms isnot indicated, the alkyl moiety or group has from 1 to 8 carbon atoms.

When referring to an alkyl moiety or group as an alkyl substituent, thatalkyl substituent to a Markush structure or another organic moiety withwhich it is associated is that chain of contiguous saturated carbonatoms covalently attached to the structure or moiety through a sp³carbon of the alkyl substituent. An alkyl substituent, as used herein,therefore contains at least one saturated moiety and may also contain orbe optionally substituted with cycloalkyl, unsaturated alkyl, aromaticor heteroaromatic moieties or groups. Thus, an alkyl substituent mayadditionally comprise one, two, three or more independently selecteddouble bonds, triple bonds or cycloalkyl, aromatic or heteroaromaticmoieties or some combination thereof, typically one double bond, onetriple bond or is substituted with one cycloalkyl, aromatic orheteroaromatic moiety. When an alkyl substituent, moiety or group isspecified, species include those derived from removing a hydrogen atomfrom a parent alkane (i.e., is monovalent) and may include methyl,ethyl, 1-propyl (n-propyl), 2-propyl (iso-propyl, —CH(CH₃)₂), 1-butyl(n-butyl), 2-methyl-1-propyl (iso-butyl, —CH₂CH(CH₃)₂), 2-butyl(sec-butyl, —CH(CH₃)CH₂CH₃), 2-methyl-2-propyl (t-butyl, —C(CH₃)₃),amyl, isoamyl, sec-amyl and other linear, cyclic and branch chain alkylmoieties.

“Alkylene,” as used herein by itself of as part of another term, refersto a saturated, branched, cyclic or straight chain hydrocarbondiradical, substituted or unsubstituted, wherein one or more of thecarbon atoms is unsaturated (i.e., is comprised of one or more sp³carbons), of the stated number of carbon atoms, typically 1-10 carbonatoms, and having two radical centers (i.e., is divalent) derived by theremoval of two hydrogen atoms from the same or two different saturated(i.e., sp³) carbon atoms of a parent alkane. Alkylene moieties furtherinclude alkyl radicals as described herein in which a hydrogen atom hasbeen removed from a saturated moiety or the radical carbon of an alkylradical to form a diradical. Typically, alkylene moieties include, butare not limited to, divalent moieties derived from removing a hydrogenatom from saturated carbon atom of a parent alkyl moiety and areexemplified by methylene (—CH₂—), 1,2-ethylene (—CH₂CH₂—), 1,3-propylene(—CH₂CH₂CH₂—), 1,4-butylene (—CH₂CH₂CH₂CH₂—), and like diradicals.Typically, an alkylene is a branched or straight chain hydrocarbontypically containing only sp³ carbons (i.e., is fully saturatednotwithstanding the radical carbon atoms).

“Cycloalkyl” as used herein is a radical of a monocyclic, bicyclic ortricyclic ring system, wherein each of the atoms forming the ring system(i.e., skeletal atoms) is a carbon atom and wherein one or more of thesecarbon atoms in each ring of the cyclic ring system is saturated (i.e.,is comprised of one or more sp³ carbons). Thus, a cycloalkyl is a cyclicarrangement of saturated carbons but may also contain unsaturated carbonatom(s) and therefore its carbocyclic ring may be saturated or partiallyunsaturated or may be fused with an aromatic ring, wherein the points offusion to a cycloalkyl and aromatic ring are to adjacent unsaturatedcarbons of the cycloalkyl moiety, group or substituent and adjacentaromatic carbons of the aromatic ring.

Unless otherwise specified, a cycloalkyl moiety, group or substituentcan be substituted with moieties described for alkyl, alkenyl, alkynyl,aryl, arylalkyl, alkylaryl and the like or can be substituted withanother cycloalkyl moieties. Cycloalkyl moieties, groups or substituentsinclude cyclopropyl, cyclopentyl, cyclohexyl, adamantly or other cyclicmoieties having only carbon atoms. Cycloalkyls further includecyclobutyl, cyclopentenyl, cyclohexenyl, cycloheptyl and cyclooctyl.Depending on its structure, a cycloalkyl substituent can be amonoradical as described above for cycloalkyl moieties or groups or adiradical (i.e., a cycloalkylene, or alternatively, carbocyclo) such as,but not limited to, cyclopropan-1,1-diyl, cyclobutan-1,1-diyl,cyclopentan-1,1-diyl, cyclohexan-1,1-diyl, cyclohexan-1,4-diyl,cycloheptan-1,1-diyl, and the like).

When cycloalkyl is used as a Markush group (i.e., a substituent) thecycloalkyl is attached to a Markush formula or another organic moietywith which it is associated through a carbon that is involved in thecarbocyclic ring system of the cycloalkyl group provided that carbon isnot an aromatic carbon of a fused ring system. When an unsaturatedcarbon of an alkene moiety comprising the cycloalkyl substituent isattached to a Markush formula with which it is associated thatcycloalkyl is sometimes referred to as a cycloalkenyl substituent. Thenumber of carbon atoms in a cycloalkyl substituent is defined by thetotal number of skeletal atoms of the ring system. That number can varyand typically ranges from 3 to 50, 1-30 or 1-20, and more typically 3-8or 3-6 unless otherwise specified, e.g., C₃₋₈ cycloalkyl means ancycloalkyl substituent, moiety or group containing 3, 4, 5, 6, 7 or 8carbocyclic carbon atoms and C₃₋₆ cycloalkyl means an cycloalkylsubstituent, moiety or group containing 3, 4, 5 or 6 carbocyclic carbonatoms. Therefore cycloalkyl substituents, moieties or groups usuallyhave 3, 4, 5, 6, 7, 8 carbon atoms in its carbocyclic ring system andmay contain exo or endo-cyclic double bonds or endo-cyclic triple bondsor a combination of both wherein the endo-cyclic double or triple bonds,or the combination of both, do not form a cyclic conjugated system of4n+2 electrons. A bicyclic ring system may share one (i.e., is a spiroring system) or two carbon atoms and a tricyclic ring system may share atotal of 2, 3 or 4 carbon atoms, typically 2 or 3.

“Alkenyl” as used herein means a substituent, moiety or group thatcomprises one or more double bond moieties (e.g., a —CH═CH— functionalgroup) or 1, 2, 3, 4, 5 or 6 or more, typically 1, 2 or 3 of suchmoieties and can be substituted with an aryl moiety or group such asbenzene, or linked normal, secondary, tertiary or cyclic carbon atoms,i.e., linear, branched, cyclic or any combination thereof unless thealkenyl substituent, moiety or group is a vinyl moiety (e.g., a —CH═CH₂functional group). An alkenyl moiety, group or substituent havingmultiple double bonds may have the double bonds arranged contiguously(i.e., a 1,3 butadienyl moiety) or non-contiguously with one or moreintervening saturated carbon atoms or a combination thereof, providedthat a cyclic, contiguous arrangement of double bonds do not form acyclic conjugated system of 4n+2 electrons (i.e., is not aromatic).

When an alkenyl moiety, group or substituent is specified, speciesinclude, by way of example and not limitation, any of the alkyl orcycloalkyl, groups moieties or substituents described herein that has anone or more endo double bonds and monovalent moieties derived fromremoval of a hydrogen atom from a sp² carbon of a parent alkenecompound. Such monovalent moieties typically include vinyl (—CH═CH₂),allyl, 1-methylvinyl, butenyl, iso-butenyl, 3-methyl-2-butenyl,1-pentenyl, cyclopentenyl, 1-methyl-cyclopentenyl, 1-hexenyl, 3-hexenyl,cyclohexenyl, and other linear, cyclic and branched chained, allcarbon-containing moieties containing at least one double bond. Whenalkenyl is used as a Markush group (i.e., is a substituent) the alkenylis attached to a Markush formula or another organic moiety with which itis associated through a double-bonded carbon (i.e., an sp² carbon) ofthe alkenyl moiety or group. The number of carbon atoms in an alkenylsubstituent is defined by the number of sp² carbon atoms of the alkenefunctional group that defines it as an alkenyl substituent and the totalnumber of contiguous saturated carbon atoms appended to each of thesesp² carbons. That number can vary and unless otherwise specified rangesfrom 1 to 50, e.g., typically 1-30 or 1-20, more typically 1-8 or 1-6,when the double bond functional group is exo in a Markush structure, orcan vary and ranges from 2 to 50, typically 2-30 or 2-20, more typically2 to 8 or 2-6, when the double bond functional group is endo to theMarkush structure. For example, C₂₋₈ alkenyl or C₂₋₈ alkenyl means analkenyl moiety containing 2, 3, 4, 5, 6, 7 or 8 carbon atoms in which atleast two are sp² carbons in conjugation with each other and C₂₋₆alkenyl or C₂₋₆ alkenyl means an alkenyl moiety containing 2, 3, 4, 5 or6 carbon atoms in which at least two are sp² carbons that are inconjugation with each other. Typically, an alkenyl substituent is aC₂-C₆ or C₂-C₄ alkenyl moiety having two sp² carbons that are inconjugation with each other.

“Alkenylene” as used herein by itself of as part of another term, refersto a substituent, moiety or group that comprises one or more double bondmoieties, as previously described for alkenyl, of the stated number ofcarbon atoms, typically 1-10 carbon atoms when the double bondfunctional group is exo to a larger moiety or 2-10, when the double bondfunctional group is endo in the alkenylene moiety, and has two radicalcenters derived by the removal of two hydrogen atoms from the same ortwo different sp² carbon atoms of a double bond moiety in a parentalkene. Alkenylene moieties further include alkenyl radicals asdescribed herein in which a hydrogen atom has been removed from the sameor different sp² carbon atom of a double bond moiety of an alkenylradical to form a diradical, or from a sp² carbon from a differentdouble bonded moiety to provide another radical carbon. Typically,alkenylene moieties include diradicals having the structure of —C═C— or—C═C—X¹—C═C— wherein X¹ is absent or is an alkylene as defined herein.

“Aryl” as used here means an organic moiety, substituent or groupdefined by an aromatic ring system or a fused ring system with no ringheteroatoms comprising 1, 2, 3 or 4 to 6 rings, typically 1 to 3 rings,wherein the rings are composed of only carbon atoms that participate ina cyclically conjugated system of 4n+2 electrons (Hückel rule),typically 6, 10 or 14 electrons some of which may additionallyparticipate in exocyclic conjugation with a heteroatom(cross-conjugated, e.g., quinone). Aryl substituents, moieties or groupsare typically formed by six, eight, ten or more aromatic carbon atoms.Aryl substituents, moieties or groups are optionally substituted.Exemplary aryls include C₆-C₁₀ aryls such as phenyl and naphthalenyl andphenanthryl. As aromaticity in a neutral aryl moiety requires an evennumber or elections it will be understood that a given range for thatmoiety will not encompass species with an odd number of aromaticcarbons. When aryl is used as a Markush group (i.e., a substituent) thearyl is attached to a Markush formula or another organic moiety withwhich it is associated through an aromatic carbon of the aryl group.Depending on the structure, an aryl group can be a monoradical (i.e.,monovalent) or a diradical (i.e., an arylene group as described herein,which is divalent).

“Arylene.” or “heteroarylene” as used herein by itself or as part ofanother term, is an aryl or heteroaryl moiety, group or substituent asdefined herein that forms two covalent bonds (i.e., it is divalent)within a larger moiety, which can be in the ortho, meta, or paraconfigurations or an aromatic diradical moiety. Exemplary arylenesinclude, but are not limited to, phenyl-1,2-ene, phenyl-1,3-ene, andphenyl-1,4-ene as shown in the following structures:

“Arylalkyl” as used herein means a substituent, moiety or group where anaryl moiety is bonded to an alkyl moiety, i.e., -alkyl-aryl, where alkyland aryl groups are as described above. e.g., —CH₂—C₆H₅,—CH₂CH(CH₃)—C₆H₅ or —CH(CH₂CH₂CH₃)—CH₂—C₆H₅. When arylalkyl is used as aMarkush group (i.e., a substituent) the alkyl moiety of the arylalkyl isattached to a Markush formula with which it is associated through a sp³carbon of the alkyl moiety.

“Alkylaryl” as used herein means a substituent, moiety or group where analkyl moiety is bonded to an aryl moiety, i.e., -aryl-alkyl, where aryland alkyl groups are as described above, e.g., —C₆H₄—CH₃ or—CH₄—CH₂CH(CH₃). When alkylaryl is used as a Markush group (i.e., asubstituent) the aryl moiety of the alkylaryl is attached to a Markushformula with which it is associated through an aromatic carbon of thearyl moiety.

“Optionally substituted alkyl”, “optionally substituted alkenyl”,“optionally substituted alkynyl”, “optionally substituted alkylaryl”.“optionally substituted arylalkyl”, “optionally substitutedheterocycle”, “optionally substituted aryl”, “optionally substitutedheteroaryl”, “optionally substituted alkylheteroaryl”, “optionallysubstituted heteroarylalkyl” and like terms refer to an alkyl, alkenyl,alkynyl, alkylaryl, arylalkyl heterocycle, aryl, heteroaryl,alkylheteroaryl, heteroarylalkyl, or other substituent, moiety or groupas defined or disclosed herein wherein hydrogen atom(s) of thatsubstituent, moiety or group has been optionally replaced with differentmoiety(ies) or group(s) or wherein an alicyclic carbon chain thatcomprise one of those substituents, moiety or group is interrupted byreplacing carbon atom(s) of that chain with different moiety(ies) orgroup(s).

Optional substituent(s) replacing hydrogen(s) in any one of theforegoing substituents, moieties or groups include those independentlyselected from the group consisting of halogen, —CN, —NH₂, —OH, —N(CH₃)₂,alkyl, fluoroalkyl, heteroalkyl, cycloalkyl, heterocycloalkyl, aryl,heteroaryl, alkoxy, aryloxy, alkylthio, arylthio, alkylsulfoxide,arylsulfoxide, alkylsulfone, and arylsulfone or those selected from thegroup consisting of halogen, —CN, —NH₂, —OH, —NH(CH₃), —N(CH₃)₂,—C(═O)OH (i.e., CO₂H), —C(═O)O-alkyl (i.e., CO₂-alkyl), —C(═O)NH₂,—C(═O)NH(alkyl), —C(═O)N(alkyl)₂, —S(═O)₂NH—, —S(═O)₂NH(alkyl),—S(═O)₂N(alkyl)₂, alkyl, cycloalkyl, fluoroalkyl, heteroalkyl, alkoxy,fluoroalkoxy, —S-alkyl and —S(═O)₂alkyl.

Typically, optional substituent(s) replacing hydrogen(s) in any one ofthe foregoing substituents, moieties or groups are independentlyselected from the group consisting of alkyl, cycloalkyl, aryl,heteroaryl, heteroalicyclic, hydroxyl, alkoxy, aryloxy, cyano, halogen,nitro, haloalkyl, fluoroalkyl, fluoroalkoxy, and amino, including mono-,di- and tri-substituted amino groups, and the protected derivativesthereof, or is selected from the group consisting of halogen, —CN, —NH₂,—OH, —NH(CH₃), —N(CH₃)₂, —CH₃, —CH₂CH₃, —CF₃, —OCH₃, and —OCF₃.Typically, any one of the foregoing substituents, moieties or groupsthat is optionally substituted by replacing one or more its hydrogenshas its hydrogen(s) replaced with one or two of the preceding optionalsubstituents, or more typically with one of the preceding optionalsubstituents. An optional substituent on a saturated aliphatic carbonatom within an acyclic or cyclic ring system further includes oxo (═O).For a phenyl or a 6-membered heteroaryl moiety, the arrangement of anytwo substituents present on the aromatic or heteroaromatic ring can beortho (o), meta (m), or para (p).

Typically, an optional substituent replacing carbon in an acyclic carbonchain is selected from the group consisting of —O—, —C(═O)—, —C(═O)O—,—S—, —S(═O)—, —S(═O)₂-, —NH—, —NHC(═O)—, —C(═O)NH—, S(═O)₂NH—,—NHS(═O)₂, —OC(═O)NH—, and —NHC(═O)O—.

Typically, any one of the foregoing substituents, moieties or groupsthat is optionally substituted by replacing one or more alicyclic carbonatoms has the carbon atom(s) replaced with one or two of the precedingoptional substituents, or more typically with one of the precedingoptional substituents.

It will be understood that an optional substituent of an alkyl oralkylene substituent, moeity or group excludes alkyl and that anoptional substituent of an alkene or alkenylene substituent, moeity orgroup excludes alkenyl as such substitutions provide moieties fallingwithin the definition of the base moieties so substituted and anoptional substituent of an alkyl or alkylene further exclude alkylene oralkenylene as such substitution provide moieties falling with thedefinition of unsaturated alkyl and unsaturated alkylene, respectively.

“Heterocycle” as used herein means a carbocycle in which one or more,but not all of the skeletal carbon atoms within the carbocyclic ringsystem are independently replaced by a heteroatom, optionallysubstituted where permitted, including N, O, S, Se, B, Si, P, whereintwo or more heteroatoms may be adjacent to each other or separated byone or more carbon atoms within the same ring system, typically by 1-3atoms. Those heteroatoms typically include N, O or S. A heterocycletypically contains a total of one to ten heteroatoms in the heterocyclicring system provided that not all of the skeletal atoms of any one ringin the heterocyclic ring system are heteroatoms, wherein each heteroatomin the ring(s), optionally substituted where permitted, is independentlyselected from the group consisting of O, S and N, with the proviso thatany one ring does not contain two adjacent O or S atoms. Whennon-aromatic, heterocycles have at least 3 atoms in their ring system,and when aromatic, heterocycles have at least 5 atoms in their ringsystem. Exemplary heterocycles are provided by Paquette, Leo A.;“Principles of Modern Heterocyclic Chemistry” (W. A. Benjamin, New York,1968), particularly Chapters 1, 3, 4, 6, 7, and 9; “The Chemistry ofHeterocyclic Compounds, A series of Monographs” (John Wiley & Sons, NewYork, 1950 to present), in particular Volumes 13, 14, 16, 19, and 28;and J. Am. Chem. Soc. 1960, 82:5545-5473 particularly 5566-5573).

When heterocycle is used as a Markush group (i.e., a substituent) theheterocycle is attached to a Markush formula or larger moiety with whichit is associated through a carbon or a heteroatom of the heterocycle,where such attachment does not result in an unstable or disallowedformal oxidation state of that carbon or heteroatom. Thus, heterocyclesin that context are monovalent moieties sometimes referred to asheterocyclyls that include heteroaryls, which have a heteroaromatic ringsystem, or a heterocycloalkyl, in which the ring system is non-aromatic,either of which may be fused with a carbocyclic, aryl or heteroarylmoiety and includes phenyl- (i.e., benzo) fused heterocycloalkyl andheteroaryl moieties, provided that when a heteroaryl moiety is fused toa heterocycloalkyl or carbocyclic moiety (i.e., when the heterocyclicportion of the fused ring system is monovalent) the resulting fused ringsystem is classified as a heteroaryl and when a heterocycloalkyl moietyis fused to a carbocyclic moiety (i.e., when the carbocyclic portion ofthe fused ring system is monovalent) the resulting fused ring system isclassified as a heterocycloalkyl.

Typically, a heterocycloalkyl is a cycloalkyl group, moiety orsubstituent wherein 1, 2 or 3 carbons of the cycloalkyl chain isreplaced with a heteroatom selected from the group consisting ofnitrogen, oxygen and sulfur and is a C₃-C₁₀ heterocycloalkyl, moretypically a C₅-C₁₀ heterocycloalkyl in which the subscript indicates thetotal number of skeletal atoms (inclusive of its carbon atoms andheteroatoms) of the ring system of the heterocycloalkyl. Non-limitingheterocycloalkyls may contain 0-2 N atoms, 0-2 O atoms or 0-1 S atoms orsome combination thereof provided at least one of said heteroatoms ispresent in the cyclic ring system and may be substituted with one or twooxo (═O) moieties, as in pyrrolidin-2-one. More typically,heterocycloalkyls include pyrrolidinyl, piperidinyl, morpholinyl andpiperazinyl.

Heteroaryls typically contain a total one to four heteroatoms in thering(s) of the heteroaryl ring system, provided that not all of theskeletal atoms of any one ring system in the heteroaryl are heteroatoms,optionally substituted where permitted, and have 0-3 N atoms, 1-3 Natoms or 0-3 N atoms with 0-1 O atoms or 0-1 S atoms, provided that atleast one heteroatom is present. A heteroaryl may be monocyclic,bicyclic or polycyclic. Monocyclic heteroaryls include C₅-C₂₄heteroaryls, typically C₅-C₁₂ or C₅-C₆ heteroaryls, in which thesubscript indicates the total number of skeletal atoms (inclusive of itscarbon atoms and heteroatoms) of the aromatic ring system of theheteroaryl. More typically a heteroaryl is an aryl moiety wherein one 1,2 or 3 of the carbon atoms of the aromatic ring(s) of a parent arylmoiety are replaced by a heteroatom, optionally substituted wherepermitted, including N, O and S, provided that not all of the skeletalatoms of any one aromatic ring system in the aryl moiety are replaced byheteroatoms and more typically are replaced by oxygen (—O—), sulfur(—S—) nitrogen (═N—) or —NR— wherein R is —H, a protecting group oralkyl, aryl or is nitrogen substituted with another organic moiety in amanner which retains the cyclic conjugated system, wherein the nitrogen,sulfur or oxygen heteroatom participates in the conjugated system eitherthrough pi-bonding with an adjacent atom in the ring system or through alone pair of electrons on the heteroatom.

In other aspects, a heteroaryl is monocyclic and typically is one having5-membered or 6-membered heteroaromatic ring system. A 5-memberedheteroaryl is a monocyclic C₅-heteroaryl containing 1 to 4 carbon atomsand the requisite number of heteroatoms within its heteroaromatic ringsystem. A 6-membered heteroaryl is a monocyclic C₆ heteroaryl containing1 to 5 carbon atoms and the requisite number of heteroatoms within itsheteroaromatic ring system. Heteroaryls that are 5-membered have four,three, two or one aromatic heteroatom(s), and heteroaryls that are6-membered include heteroaryls having four, three, two or one aromaticheteroatom(s). C₅-heteroaryls are monovalent moieties derived fromremoving a hydrogen atom from an aromatic carbon or an electron from anaromatic heteroatom, where permitted, from a parent heterocycle compoundincluding pyrrole, furan, thiophene, oxazole, isoxazole, thiazole,isothiazole, imidazole, pyrazole, triazole and tetrazole. C₆heteroaryls, which are 6-membered, are exemplified by monovalentmoieties derived from removing a hydrogen atom from an aromatic carbonor an electron from an aromatic heteroatom, where permitted, from thefollowing parent heterocycle compounds: pyridine, pyridazine,pyrimidine, and triazine.

A “5-membered nitrogen-containing heteroaryl”, 5-membered nitrogenheteroaryl and like terms refer to a 5-membered heteroaromatic moietycontaining at least one nitrogen atom it its aromatic ring system and isa monocyclic heteroaryl or is fused to an aryl or another heteroarylring system and may contain one or more other independently selectedheteroatoms such as N, O or S. Exemplary 5-membered nitrogen heteroarylsinclude thiazole, imidazole, oxazole, and triazole and is typicallythiazole or oxazole, more typically thiazole.

“Heteroarylalkyl” as used herein means a substituent, moiety or groupwhere a heteroaryl moiety is bonded to an alkyl moiety, i.e.,-alkyl-heteroaryl, where alkyl and heteroaryl groups are as describedabove. When heteroarylalkyl is used as a Markush group (i.e., asubstituent) the alkyl moiety of the heteroarylalkyl is attached to aMarkush formula with which it is associated through a sp³ carbon of thealkyl moiety.

“Alkylheteroaryl” as used herein means a substituent, moiety or groupwhere a heteroaryl moiety is bonded to an alkyl moiety, i.e.,-heteroaryl-alkyl, where heteroaryl and alkyl groups are as describedabove. When heteroarylalkyl is used as a Markush group (i.e., asubstituent) the heteroaryl moiety of the heteroarylalkyl is attached toa Markush formula with which it is associated through a sp² carbon orheteroatom of the alkyl moiety.

“O-linked moiety”, “O-linked substituent” and like terms as used hereinrefers to a group or substituent that is attached to a moiety directlythrough an oxygen atom of the group or substituent. An O-linked groupmay be monovalent including groups such as —OH, acetoxy (i.e.,—OC(═O)CH₃), acyloxy (i.e., —OC(═O)R^(a), wherein R^(a) is —H,optionally substituted alkyl, optionally substituted cycloalkyl,optionally substituted alkenyl, optionally substituted alkynyl,optionally substituted aryl, optionally substituted heteroaryl oroptionally substituted heterocycle), and further include monovalentgroups such as alkyloxy, optionally substituted, wherein the alkylmoiety is saturated or unsaturated, and other ethers including aryloxy(Aryl-O—), phenoxy (Ph-O—), heteroaryloxy (Heteroaryl-O—), optionallysubstituted and silyloxy, (i.e., R₃SiO—, wherein each R independently isalkyl or aryl, optionally substituted), and —OR^(PR), wherein R^(PR) isa protecting group as previously defined, or an O-linked group may bedivalent, i.e., ═O or —X—(CH₂)_(n)—Y—, wherein X and Y independently areS and O and n is 2 to 3, to form a spiro ring system with the carbon towhich X and Y are attached. Typically, a O-linked substituent is amonovalent moiety selected from the group consisting of —OH, —OC(═O)CH₃,—OC(═O)R^(a), C₁-C₆ saturated alkyl ether and C₃-C₆ unsaturated ether,wherein R^(a) is C₁-C₆ saturated alkyl or C₃-C₆ unsaturated alkyl orC₂-C₆ alkenyl or is selected from that group excluding —OH. Otherexemplary O-linked substituent are provided by definitions forcarbamate, ether and carbonate as disclosed herein

“Halogen” or “halo” as used herein means fluorine, chlorine, bromine oriodine and is typically —F or —Cl.

“Protecting group” as used here means a moiety that prevents or reducesthe ability of the atom or functional group to which it is linked fromparticipating in unwanted reactions. Typical protecting groups for atomsor functional groups are given in Greene (1999), “Protective groups inorganic synthesis, 3^(rd) ed.”, Wiley Interscience. Protecting groupsfor heteroatoms such as oxygen, sulfur and nitrogen are sometime used tominimize or avoid unwanted their reactions with electrophilic compounds.Other times the protecting group is used to reduce or eliminate thenucleophilicity and/or basicity of the unprotected heteroatom.Non-limiting examples of protected oxygen are given by —OR^(PR), whereinR^(PR) is a protecting group for hydroxyl, wherein hydroxyl is typicallyprotected as an ester (e.g., acetate, propionate or benzoate). Otherprotecting groups for hydroxyl avoid interfering with thenucleophilicity of organometallic reagents or other highly basicreagents, where hydroxyl is typically protected as an ether, includingalkyl or heterocycloalkyl ethers, (e.g., methyl or tetrahydropyranylethers), alkoxymethyl ethers (e.g., methoxymethyl or ethoxymethylethers), optionally substituted aryl ethers, and silyl ethers (e.g.,trimethylsilyl (TMS), triethylsilyl (TES), tert-butyldiphenylsilyl(TBDPS), tert-butyldimethylsilyl (TBS/TBDMS), triisopropylsilyl (TIPS)and 12-(trimethylsilyl)ethoxyl-methylsilyl (SEM)). Nitrogen protectinggroups include those for primary or secondary amines as in —NHR^(PR) or—N(R^(PR))₂—, wherein least one of R^(PR) is a nitrogen atom protectinggroup or both R^(PR) together comprise a protecting group.

A protecting group is a suitable protecting when it is capable ofpreventing or avoiding unwanted side-reactions or premature loss of theprotecting group under reaction conditions required to effect desiredchemical transformation elsewhere in the molecule and duringpurification of the newly formed molecule when desired, and can beremoved under conditions that do not adversely affect the structure orstereochemical integrity of that newly formed molecule. By way ofexample and not limitation, a suitable protecting group may includethose previously described for protecting functional groups. In someaspects a suitable protecting group is typically a protecting group usedin peptide coupling reactions. For example, a suitable protecting groupfor nitrogen is an acid-labile carbamate protecting group such as BOC.

“Ester” as used herein means a substituent, moiety or group thatcontains a —C(═O)—O— structure (i.e., ester functional group) whereinthe carbon atom of the structure is not directly connected to anotherheteroatom and is directly connected to —H or another carbon atom of anorganic moiety, and the monovalent oxygen atom is attached to the sameorganic moiety to provide a lactone or a different organic moiety.Typically, esters comprise or consist of organic moieties containing1-50 carbon atoms, typically 1-20 carbon atoms or more typically 1-8carbon atoms and 0 to 10 independently selected heteroatoms (e.g., O, S,N, P, Si, but usually O, S and N), typically 0-2 where the organicmoieties are bonded through the —C(O)—O— structure (i.e., through theester functional group). When an ester is a substituent or variablegroup of a Markush structure that substituent is bonded to the structurethrough the monovalent oxygen atom of the ester functional group. Inthose instances the organic moiety attached to the carbonyl carbon ofthe ester functional group comprises any one of the organic groupsdescribed herein, e.g., C₁-C₂₀ alkyl moieties. C₂-C₂₀ alkenyl moieties,C₂-C₂₀ alkynyl moieties. C₆-C₂₄ aryl moieties, C₅-C₂₄ heterocycles orsubstituted derivatives of any of these, e.g., comprising 1, 2, 3, 4 ormore substituents, where each substituent is independently chosen.Exemplary esters include, by way of example and not limitation, acetate,propionate, isopropionate, isobutyrate, butyrate, valerate, isovalerate,caproate, isocaproate, hexanoate, heptanoate, octanoate, phenylacetateesters or benzoate esters or have the structure of —OC(═O)R^(a) whereinR^(a) is as defined for acyloxy O-linked substituent and is typicallyselected from the group consisting of methyl, ethyl, propyl, iso-propyl,3-methyl-prop-1-yl, 3,3-dimethyl-prop-1-yl and vinyl. Ester substituentsas disclosed herein are exemplary monovalent 0-linked substituents.

“Ether” as used herein means an organic moiety, group or substituentthat comprises 1, 2, 3, 4 or more —O— (i.e., oxy) moieties that are notbonded to carbonyl moiety(ies), usually 1 or 2, wherein no two —O—moieties are immediately adjacent (i.e., directly attached) to eachother. Typically, an ether structure is comprised or consists of theformula —O-organic moiety wherein organic moiety is as described for anorganic moiety bonded to an ester functional group. More typically, anether moiety, group or substituent has the formula of —O-organic moietywherein the organic moiety is as described herein for an optionallysubstituted alkyl group. When ether is used as a Markush group (i.e., anether substituent) the oxygen of the ether functional group is attachedto a Markush formula with which it is associated. When ether is a usedas substituent in a Markush group it is sometimes designated as an“alkoxy” group, which is an exemplary O-linked substituent. Alkoxyincludes C₁-C₄ ether substituents such as, by way of example and notlimitation, methoxy, ethoxy, propoxy, iso-propoxy, butoxy and allyloxy.

“Amide” or “carboxamide” as used here means an moiety that contains aR—C(═O)N(R)— or —C(═O)N(R)₂ structure (i.e., amide or carboxamide orfunctional group, respectively) with no other heteroatom directlyattached to the carbonyl carbon of the structure and where R,independently selected, is hydrogen, a protecting group or an organicmoiety as described herein for an organic moiety bonded to an esterfunctional group and is typically an optionally substituted alkyl group.Typically, hydrogen or an organic moiety, independently selected from R,is bonded to the carboxamide or amide functional group, wherein thatorganic moiety is also as described herein for an organic moiety bondedto an ester functional group. When bonded to an organic moiety theresulting structure is represented by R—C(═O)N(R)-organic moiety ororganic moiety-C(═O)N(R)₂. When an amide is recited as a variable for aMarkush structure, the amide nitrogen is bonded to that structure. Forcarboxamide substituents the carbonyl carbon of the amide functionalgroup is bonded to the Markush structure. Amides and carboxamides aretypically prepared by condensing an acid halide, such an acid chloridewith a molecule containing a primary or secondary amine. Alternatively,amide coupling reactions well-known in the an of peptide synthesis,which oftentimes proceed through an activated ester of a carboxylicacid-containing molecule, are used. Exemplary preparations of amidebonds through peptide coupling methods is provided in Benoiton (2006)Chemistry of peptide synthesis CRC Press, Bodansky “Peptide synthesis: Apractical textbook” (1988) Springer-Verlag; Frinkin, M. et al. “PeptideSynthesis” Ann. Rev. Biochem. (1974) 43: 419-443. Reagents used in thepreparation of activated carboxylic acids is provided in Han, et al.“Recent development of peptide coupling agents in organic synthesis”Tet. (2004) 60: 2447-2476.

“Carbonate” as used here means a substituent, moiety or group thatcontains a —O—C(═O)—O— structure (i.e., carbonate functional group).Typically, carbonate groups as used here comprise or consist of anorganic moiety, wherein the organic moiety is as described herein for anorganic moiety bonded to an ester functional group, bonded through the—O—C(═O)—O— structure, e.g., organic moiety-O—C(═O)—O—. When carbonateis used as a Markush group (i.e., a substituent) one of the singlybonded oxygen atoms of the carbonate functional group is attached to aMarkush formula with which it is associated and the other is bonded to acarbon atom of an organic moiety as previously described for an organicmoiety bonded to an ester functional group. In such instances carbonateis an exemplary O-linked substituent.

“Carbamate” or “urethane” as used here means a substituent, moiety orgroup that contains a carbamate functional represented by—O—C(═O)N(R^(a))— or —O—C(═O)N(R^(a))₂, and include —O—C(═O)NH(optionally substituted alkyl) or —O—C(═O)N (optionally substitutedalkyl)₂, which are exemplary carbamate substituents, wherein R^(a) andoptionally substituted alkyl are independently selected wherein R^(a),independently selected, is hydrogen, a protecting group or an organicmoiety, wherein the organic moiety is as described herein for an organicmoiety bonded to an ester functional group and is typically anoptionally substituted alkyl. Typically, carbamate groups as used hereincomprise or consist of an organic moiety, independently selected fromR^(a), wherein the organic moiety is as described herein for an organicmoiety bonded to an ester functional group, bonded through the—O—C(═O)—N(R^(a))— structure, wherein the resulting group has theformula of organic moiety-O—C(═O)—N(R^(a))— or —O—C(═O)—N(R^(a))-organicmoiety. When carbamate is used as a Markush group (i.e., a substituent),the singly bonded oxygen (O-linked) or nitrogen (N-linked) of thecarbamate functional group is attached to a Markush formula with whichit is associated. The linkage of the carbamate substituent is eitherexplicitly stated (N- or O-linked) or implicit in the context to whichthis substituent is referred. O-linked carbamates described herein areexemplary monovalent O-linked substituents.

“Antibody” as used herein is used in the broadest sense and specificallycovers intact monoclonal antibodies, polyclonal antibodies, monospecificantibodies, multispecific antibodies (e.g., bispecific antibodies), andantibody fragments that exhibit the desired biological activity providedthat the antibody fragment have the requisite number of attachment sitesfor a drug-linker. The native form of an antibody is a tetramer andconsists of two identical pairs of immunoglobulin chains, each pairhaving one light chain and one heavy chain. In each pair, the light andheavy chain variable regions (VL and VH) are together primarilyresponsible for binding to an antigen. The light chain and heavy chainvariable domains consist of a framework region interrupted by threehypervariable regions, also called “complementarity determining regions”or “CDRs.” The constant regions may be recognized by and interact withthe immune system (see, e.g., Janeway et al., 2001, Immunol. Biology,5th Ed., Garland Publishing, New York). An antibody can be of any type(e.g., IgG, IgE, IgM, IgD, and IgA), class (e.g., IgG1, IgG2, IgG3,IgG4, IgA1 and IgA2) or subclass. The antibody can be derived from anysuitable species. In some embodiments, the antibody is of human ormurine origin. An antibody can be, for example, human, humanized orchimeric. An antibody or antibody fragment thereof, is an exemplarytargeting agent that corresponds to or is incorporated into an LDC ofthe present invention as an antibody Ligand Unit.

In some aspects an antibody selectively and specifically binds to anepitope on hyper-proliferating cells or hyper-stimulated mammalian cells(i.e., abnormal cells), wherein the epitope is preferentially displayedby or is more characteristic the abnormal cells in contrast to normalcells, or is preferentially displayed by or is more characteristic ofnormal cells in the vicinity of abnormal cells in contrast to normalcells not localized to the abnormal cells. In those aspects themammalian cells are typically human cells. Other aspects of antibodiesincorporated into Ligand Units are described by embodiments forLigand-Drug Conjugates

“Monoclonal antibody” as used herein refers to an antibody obtained froma population of substantially homogeneous antibodies, i.e., theindividual antibodies comprising the population are identical except forpossible naturally-occurring mutations that may be present in minoramounts. Monoclonal antibodies are highly specific, being directedagainst a single antigenic site. The modifier “monoclonal” indicates thecharacter of the antibody as being obtained from a substantiallyhomogeneous population of antibodies, and is not to be construed asrequiring production of the antibody by any particular method.

“Cytotoxic activity” as used herein refers to a cell-killing effect of adrug, Ligand-Drug Conjugate, or an intracellular metabolite of aLigand-Drug Conjugate. Cytotoxic activity may be expressed as the IC₅₀value, which is the concentration (molar or mass) per unit volume atwhich half the cells survive.

“Cytostatic activity” as used herein refers to an anti-proliferativeeffect of a drug, Ligand-Drug Conjugate, or an intracellular metaboliteof a Ligand-Drug Conjugate that is not dependent on cell killing butwhose effect is due to inhibition of cell division ofhyper-proliferating cells, hyper-stimulated immune cells or otherabnormal or unwanted cells.

The terms “specific binding” and “specifically binds” mean that anantibody or antibody Ligand Unit in an LDC as the targeting moiety iscapable of binding, in a selective or highly selective manner, with itscorresponding target antigen and not with a multitude of other antigens.Typically, the antibody or antibody derivative binds with an affinity ofat least about 1×10⁻⁷ M, and preferably 10⁻⁸ M to 10⁻⁹ M, 10⁻¹⁰ M, 10⁻¹¹M, or 10⁻¹² M and binds to the predetermined antigen with an affinitythat is at least two-fold greater than its affinity for binding to anon-specific antigen (e.g., BSA, casein) other than for aclosely-related antigen.

“Ligand-Drug Conjugate” or “LDC” as the term is used herein refers to aconstruct comprised of a Ligand Unit from a targeting agent and aquaternized tertiary amine-containing Drug Unit (D⁺) corresponding instructure to a tertiary-amine containing drug that are bonded to eachother through a Linker Unit, wherein the LDC selectively binds to atargeted moiety through its targeting Ligand Unit. In some instances,the term LDC is a plurality (i.e., composition) of individual LDCcompounds differing primarily by the number of D⁺ units bonded to eachLigand Unit and/or the location on the Ligand Unit at which the D⁺ unitsare bound. In other instances the term LDC applies to an individualmember or compound of the composition.

“Targeting agent” as the term is used herein is a moiety correspondingto or incorporated as a Ligand Unit in a Ligand Drug Conjugate so thatthe Ligand Unit is the targeting moeity of the Conjugate that is capableof binding selectively to a targeted moiety typically present on,within, or in the vicinity of hyper-proliferating cells,hyper-stimulated immune cells or other abnormal or unwanted cells incomparison to other moieties present on, within, or in the vicinity ofnormal cells where these abnormal or unwanted cells are typically notpresent. Sometimes a targeted moiety is present on, within, or in thevicinity of abnormal in greater abundance in comparison to normal cellsor the environment of normal cells where abnormal cells are typicallynot present. In some instances the targeting agent is an antibody thatspecifically binds to an accessible antigen characteristic of anabnormal cell or is an accessible antigen that is particular to thesurrounding environment in which these cells are found. In otherinstances the targeting agent is a ligand that specifically binds to anaccessible receptor characteristic of, or in greater abundance on,abnormal cells or other unwanted cells, or is an accessible receptorthat is particular to cells of the surrounding environment in whichabnormal cells are found. Typically a targeting agent is an antibody asdefined herein that binds selectively to a targeted moiety of anabnormal or unwanted mammalian cell, more typically a targeted moiety ofan abnormal or unwanted a human cell.

“Target cells” or “targeted cells” as the term is used herein are theintended cells (i.e., abnormal or other unwanted cells) to which an LDCis designed to interact in order to inhibit the proliferation or otherunwanted activity of the intended cells. In some instances the targetedcells are hyper-proliferating cells or hyper-activated immune cells,which are exemplary abnormal cells. Typically those abnormal cells aremammalian cells and more typically are human cells. In other instancesthe targeted cells are within the vicinity of abnormal or unwanted cellsso that action of the LDC on the nearby cells has an intended effect onthe abnormal or unwanted cells. For example, the nearby cells may beepithelial cells that are characteristic of the abnormal vasculature ofa tumor. Targeting of those vascular cells by an LDC will either have acytotoxic or cytostatic effect on these cells by inhibiting nutrientdelivery to the abnormal cells of the tumor or indirectly have acytotoxic or cytostatic effect on the abnormal cells, and/or have adirect a cytotoxic or cytostatic effect on the abnormal cells byreleasing D⁺ as a tubulysin drug compound (D) in the vicinity of thesecells.

“Targeted moiety” as the term is used herein is a moiety preferentiallyrecognized by a targeting agent or Ligand Unit of a Ligand-DrugConjugate corresponding to or incorporating that targeting agent (i.e.,is selectively bound by the Ligand Unit) and is present on, within or inthe vicinity of targeted cells. Sometimes the targeted moiety is anantigen accessible to selective binding by an antibody, which is anexemplary targeting agent that corresponds to or is incorporated in aLDC as an antibody Ligand Unit. In those instances, such an antigen is acell-surface protein present on abnormal cells or other unwanted cells,or is present on cells that are particular to the surroundingenvironment in which the abnormal or unwanted cells are found, such asvascular cells that are characteristic of the environment ofhyper-proliferating cells in a tumor. More typically, the antigen is acell-surface protein of an abnormal cell or other unwanted cell that iscapable of internalization upon binding with its cognate targeting agentor moeity. In other instances the targeting agent is a ligand for anextracellularly accessible cell membrane receptor that may beinternalized upon binding of the targeting moiety or is capable ofpassive or facilitative transport of the LDC targeting the cell-surfacereceptor so that the receptor is the targeted moeity. In some aspects,the targeted moiety is present on abnormal mammalian cells or onmammalian cells characteristic of the environment of such abnormalcells.

“Antibody-drug conjugate” or “ADC” as the term is used herein refers toa Ligand Drug Conjugate wherein the targeting agent corresponding to oris incorporated into its Ligand Unit is an antibody, thereby defining anantibody Ligand Unit, wherein the antibody Ligand Unit is covalentlyattached to a quaternized drug unit (D⁺), typically through anintervening Linker Unit. Oftentimes the term refers to a collection(i.e., population or plurality) of conjugate compound having the sameantibody Ligand Unit, quaternized Drug unit, and Linker Unit, but havingvariable loading and/or distribution of the linker-drug moieties foreach antibody (as, for example, when the number of quaternized DrugUnits (D⁺) of any two ADC compounds in a plurality of such compounds isthe same but the location of their sites of attachment to the targetingmoiety differ). In those instances an ADC is described by the averageddrug loading of the Conjugate compounds. An ADC obtained from themethods described herein have the general structure of Ab-L_(B)-L_(O)-D⁺wherein -L_(B)-L_(O)- defines the Linker Unit in which L_(B) is a ligandcovalent binding moiety or Ligand Covalent Binding Unit sometimesreferred to as a primary linker (L_(R)), so named because that moiety orunit is required to be present in a Linker Unit of an ADC, and L_(O) isa secondary linker susceptible to enzymatic (e.g., protease orglycosidase) or non-enzymatic (e.g., reductive or hydrolytic) cleavage.In some instances that cleavage is enhanced in the environment ofabnormal cells or occurs subsequent to intracellular internalization ofthe ADC subsequent to binding of the ADC's targeting antibody LigandUnit to its cognate antigen; D⁺ is a quaternized Drug Unit and istypically is derived from quaternization of a tertiary amine-containingdrug (D), or corresponds to the quaternized from of D wherein D⁺ isreleased as the tertiary amine-containing drug as a result of thatenzymatic or non-enzymatic action on L_(O).

The average number of quaternized Drug Units per antibody Ligand Unit,or fragment thereof, in an ADC composition (i.e., an averaged number fora population of ADC conjugate compounds that differ primarily by thenumber of conjugated quaternized Drug Units on the antibody Ligand Unitin each of the ADC compounds that are present in that population and/orby their location) when the Linker Units are not branched is designatedas p or when the linkers are branched, p is the average number ofdrug-linker moieties attached to the antibody Ligand Unit. In eithercontext p is a number ranging from about 2 to about 24 or about 2 toabout 20 and is typically about 2, about 4, or about 8. In othercontexts p represents the number of quaternized Drug Units when theLinker Units are not branched, or the number of quaternized drug linkermoieties when the Linker Units are branched, that are covalently bondedto a single antibody Ligand Unit of an ADC within a population ofantibody-drug conjugate compounds in which the compounds of thatpopulation may primarily differ by the number and/or location of theconjugated quaternized Drug Units or quaternized drug linker moieties ineach of the ADC compounds. In that context p is designated as p′ and isan integer ranging from 1 to 24 or from 1 to 20, typically from 1 to 12or 1 to 10, and more typically from 1 to 8.

The average number of quaternized Drugs Units per Ligand Unit in apreparation from a conjugation reaction may be characterized byconventional means such as mass spectroscopy, ELISA assay, HIC and/orHPLC. The quantitative distribution of conjugate compounds in terms ofp′ may also be determined. In some instances, separation, purification,and characterization of homogeneous Ligand-Drug Conjugate compounds inwhich p′ is a certain value from a Ligand-Drug Conjugate compositionfrom those with other drug loadings may be achieved by means such asreverse phase HPLC or electrophoresis.

“Antigen” is an entity that is capable of selective binding to anunconjugated antibody or a fragment thereof or to an ADC comprising anantibody Ligand Unit corresponding to or incorporating that antibody orfragment thereof. In some aspects, the antigen is anextracellularly-accessible cell-surface protein, glycoprotein, orcarbohydrate preferentially displayed by abnormal or other unwantedcells in comparison to normal cells. In some instances the unwantedcells having the antigen are hyper-proliferating cells in a mammal. Inother instances, the unwanted cells having the antigen arehyper-activated immune cells in a mammal. In other aspects, thespecifically bound antigen is present in the particular environment ofhyper-proliferating cells or hyper-activated immune cells in a mammal incontrast to the environment typically experienced by normal cells in theabsence of such abnormal cells. In still other aspects the cell-surfaceantigen is capable of internalization upon selective binding of an ADCcompound and is associated with cells that are particular to theenvironment in which hyper-proliferating or hyper-stimulated immunecells are found in the absence of such abnormal cells. An antigen is anexemplary targeted moiety of an LDC wherein its targeting Ligand Unitcorresponds to or incorporates an antibody to a targeted antigen and iscapable of preferentially recognizing that antigen through selectivebinding.

Antigens associated with hyper-proliferating cells that are cell-surfaceaccessible to an ADC include by way of example and not limitation CD19,CD70, CD30, CD33, NTB-A, αvβ6, and CD123.

“Ligand Unit” is a moiety comprising a Ligand Drug Conjugate that iscapable of binding selectively to its cognate targeted moiety and issometimes referred to as the targeting moeity of a LDC. A Ligand Unitincludes without limitation those of targeting agents such as receptorligands, antibodies to cell-surface antigens and transporter substrates.Sometimes, the receptor, antigen or transporter to be bound by a LDC ispresent in greater abundance on abnormal cells in contrast to normalcells. Other times the receptor, antigen or transporter to be bound byan LDC is present in greater abundance on normal cells that are peculiarto the environment of abnormal cells in contrast to normal cells of theperiphery. Various aspects of Ligand Units are further described by theof the embodiments of the invention.

“Ligand covalent binding moiety” or “Ligand Covalent Binding Unit” is amoiety or component of a Linker Unit (LU) in an LDC that is covalentlyattached to the Ligand Unit that targets the abnormal or unwanted cellsor their environment and to the remainder of the Linker Unit and isderived from reaction of the corresponding L_(B)′ moeity or component ina Linker Unit precursor with a targeting agent. For example, when L_(B)′is comprised of a maleimide moiety, reaction of that moiety with areactive sulfhydryl group of a targeting agent converts L_(B)′ to L_(B),which is comprised of a thio substituted succinimide moiety, bound to aLigand Unit, which corresponds to or incorporates the targeting agent.In another example, when L_(B)′ is comprised of an activated carboxylicacid functional group, reaction of that functional group with an epsilonamino group of a lysine in a targeting agent converts the functionalgroup to an amide, wherein that amide comprises the L_(B) moietycovalently attached to a Ligand Unit that corresponds to or incorporatesthat targeting agent. Other L_(B) moieties or units and their conversionfrom L_(B)′-containing moieties or units are described in theembodiments of the invention. In some instances a targeting agent isderivitized with a bi-functional molecule to provide an intermediatethat is condensed with a ligand covalent binding precursor (L_(B)′)moiety or unit. As a result of that condensation the L_(B) moiety orunit so formed has atoms attributable to the bi-functional molecule andL_(B)′.

“Ligand covalent binding moiety precursor” or “Ligand Covalent BindingUnit precursor” is a moiety or component of a Linker Unit, orsubstructure thereof used in the preparation of a Linker Unit, that iscapable of covalent binding to a targeting agent during the preparationof an LDC whereupon the ligand binding (L_(B)′) moiety or unit precursoris converted to a ligand covalent binding (L_(B)) moiety or unitcovalently attached to a Ligand Unit corresponding to or incorporatingthe targeting agent. In some aspects a L_(B)′ moiety typically has afunctional group capable of reacting with a nucleophile or electrophilenative to an antibody or fragment thereof or is introduced into anantibody by chemical transformation or genetic engineering. In someaspect the nucleophile is an N-terminal amino group of a peptidecomprising an antibody or the epsilon amino group of a lysine residue ofan antibody. In other aspects the nucleophile is a sulfhydryl group of acysteine residue of an antibody introduced by genetic engineering orfrom chemical reduction of an interchain disulfide of an antibody. Insome aspects the electrophile is an aldehyde introduced by selectiveoxidation of an antibody's carbohydrate moiety or is a ketone from anunnatural amino acid introduced into an antibody using a geneticallyengineered tRNA/tRNA synthetase pair. Those and other methods arereviewed by Behrens and Liu “Methods for site-specific drug conjugationto antibodies” mAB (2014) 6(1): 46-53.

“Linker Unit” as the term is used herein refers to an organic moiety ina Ligand Drug Conjugate (LDC) intervening between and covalentlyattached to a quaternized drug unit (D⁺) and Ligand Unit or to anorganic moiety of a Drug Linker compound intervening between andcovalently attached to a quaternized drug unit (D⁺) and a ligandcovalent binding precursor (L_(B)′) moiety or unit. Typically, a LinkerUnit (LU) of a LDC or Drug Linker compound is comprised of a ligandcovalent binding (L_(B)) moiety or unit or a ligand covalent bindingprecursor (L_(B)′) moiety or unit, respectively, and a secondary linker(L_(O)) as described herein. In some aspects the ligand covalent bindingprecursor or unit contains a maleimide (M¹) moiety. Attachment of thetargeting agent through M¹ resulting in covalent attachment of thecorresponding Ligand Unit to a Linker Unit occurs through a cysteinesulfhydryl group of the targeting agent by Michael addition of thesulfhydryl group sulfur atom to the maleimide ring system of M¹. As aresult of that addition a succinimide (M²) moiety having a sulfursubstituted succinimide ring system is obtained. Subsequent hydrolysisof that ring system, either spontaneously or under controlledconditions, as when that system is part of a self-stabilizing linker(L_(SS)) moiety, results in a succinic acid-amide (M³) moiety, which isan exemplary self-stabilized (L_(S)) moiety, as further describedherein. Also covalently bonded to L_(B) or L_(B)′, which are primarylinker (L_(R) moieties), is a secondary linker (L_(O)) moiety, whichfurther intervenes between the Ligand Unit and quaternized Drug Unit(D⁺) in an LDC or between L_(B)′ and D⁺ in a Drug Linker compound,wherein covalently bonding to L_(R) is through intermediacy of an ether,ester, carbonate, urea, disulfide, amide or carbamate functional group,more typically through an ether, amide or carbamate functional group.

“Parallel Connector Unit” as used herein refers to a branched LinkerUnit component that connects a PEG Unit in parallel orientation to aquaternized Drug Unit (D⁺). As used herein, the phrase “parallelorientation”, “parallel placement”, “parallel connection” and like termsrefers to a configuration wherein the parallel-placed orparallel-oriented or parallel-connected components are attached to aparallel connecter unit (L^(P)) in such a manner that each component hasone end tethered to L_(P) and one free end. Typically L_(P) connects aquaternized Drug Unit (D⁺) through one or more Linker Unit components,such as A_(O)-W—Y—, —or A_(O)-Y(W′)— wherein A_(O) is optionallypresent, and a PEG Unit so that the quaternized Drug and PEG Units arein a parallel orientation such that the hydrophobicity of thequaternized Drug Unit is masked to an effective extent by the PEG Unit.Only those PEG Units required for masking hydrophobicity for a givenLU-D⁺ moiety (i.e. quaternized drug linker moiety) need be in parallelorientation to its quaternized Drug Unit, which does not necessarilyrequire all of the quaternized Drug Units and polyethylene glycol (PEG)units connected to L^(P) be in parallel orientations to one another.Thus, one PEG Unit may effectively mask the hydrophobicity or 1, 2, 3, 4or more quaternized Drug Units, typically 1 to 4 D⁺ and more typically 1or 2 D⁺.

The term “parallel” is used herein to denote branching of two componentsof a Ligand-Drug Conjugate (LDC) or Drug Linker compound from a L^(P)that comprises the LDC or Drug Linker compound and is not being used todenote that the two components are side-by-side in space or have thesame distance between them throughout some or their entire lengths. ALDC or Drug Linker compound having a PEG Unit that is in a parallelorientation in relation to a quaternized Drug Unit of the LDC or DrugLinker compound refers to a LDC or Drug Linker compound comprising a PEGUnit having one its termini connected to a component of a Linker Unit(i.e., a Parallel Connector Unit) and one or more free untetheredterminus (or termini). The free untethered terminus of the PEG Unit whenattached to L^(P) can take the form, for example, of an unreactedfunctional group, e.g., alkoxy, carboxylic acid, alkylenecarboxylicacid, alcohol, or other functional group. In instances where aparallel-oriented PEG component is itself branched and thus has multipleends, it still has only one tethered end to L^(P). The parallelorientation of the PEG Unit in relationship to D⁺ also acts to minimizethe number of atoms between the Ligand Unit and the Drug Unit as theatoms of the PEG Unit are not interposed between D⁺ and the Ligand Unit.

An exemplary graphical representation of a LDC having a PEG Unit that isin a parallel (i.e., branched) orientation in relation to thequaternized Drug Unit is as follows:

wherein subscript n′ ranges from 1 to 24.

“Primary linker” as used is a ligand covalent binding (L_(B)) moiety orunit, or a ligand covalent binding (L_(B)′) precursor moiety or unit,and is present as a component of a Linker Unit of a LDC, or as acomponent of a L_(B)′-containing moiety such as L_(B)′-L_(O)- orL_(B)′-L_(O)-D⁺ in a Drug Linker compound. A L_(B)′ primary linker iscomprised of a reactive functional group capable of reacting with anelectrophilic or nucleophillic functional group of a targeting agent. Asa result of that reaction, the targeting agent becomes covalently bondedas a Ligand Unit to L_(B) of a primary linker through a functional groupderived from the reactive functional group of L_(B)′.

“Secondary linker” moiety as used herein refers to an organic moiety ina Linker Unit wherein the secondary linker (L_(O)) is covalentlyattached to a L_(B) or L_(B)′ moiety (i.e., a primary linker unit)through intermediacy of a functional group between the L_(B) or L_(B)′moiety and the remainder of the Linker Unit to which a quaternized DrugUnit may be covalently attached. In a LDC, the secondary linker is alsocovalently attached to a quaternized Drug Unit (D⁺) through the benzylicposition of a PAB or PAB-type self-immolating moiety that comprises aself-immolative Spacer unit. In addition to such a Spacer unit (Y),secondary linkers are comprised of a Cleavable (W or W′), wherein W, Yand D⁺ or W′, Y and D⁺ are arranged either in a linear or orthogonalrelationship, respectively, and is further comprised of a -L^(P)(PEG)-moiety and first optional Stretcher unit (A), and/or a Branching Unit,in which the latter may be replaced with a second optional StretcherUnit (A_(O)) when LU is attached to only one quaternized drug unit (D⁺).When present, A interconnects L_(B)′, or L_(B) derived therefrom, withthe remainder of the secondary linker through -L^(P)(PEG)-, or throughA_(O), or B, when either is present, or interconnects D⁺ and-L^(P)(PEG)- through —W—Y— or —Y(W′)— when B and A_(O) are absent.

In an LDC, L_(O) is comprised of a self-immolative Spacer unit (Y),which contains a self-immolating moiety, and is covalently attached to aCleavable Unit (W or W′) such that cleavage of W or W′ under conditionsmore likely experienced by abnormal cells results in self-destruction ofthe self-immolating moiety with concomitant release of D⁺ as a drugcompound (D). Alternatively, that cleavage may be affected within thevicinity of those abnormal cells, in comparison to normal cells in theirnormal environment. Typically, that self-destruction occurs through a1,6-elimination in an self-immolative moiety as described herein. Inthose instances a self-immolative moeity of a self-immolative SpacerUnit is attached to a tertiary amine-containing drug throughquaternization of that drug's tertiary amine nitrogen.

A secondary linker (L_(O)) when bonded to D⁺ in a Linker Unit attachedto only one D⁺ is typically represented by the structure of (1) or (2):

wherein the variable groups are as defined herein. In some aspects ofthe invention Y in structure (1) is comprised or consists of aself-immolative moiety (SI) as described herein substituted with W andD⁺. In other aspects of the invention Y in structure (2) is comprised orconsists of a self-immolating moiety as described herein substitutedwith D⁺ through a quaternary amine nitrogen of a tubulysin compound andis further substituted with W′ and Ligand-L_(B)-A_(a)-L^(P)(PEG)-A_(O)-or L_(B)′-A_(a)-L^(P)(PEG)-A_(O)- in a Ligand Drug Conjugate or DrugLinker compound, respectively, wherein A_(O) is optionally present(i.e., A_(O) is bonded to a self-immolative moeity of Y when A_(O) ispresent) or is further substituted by L_(B)-A_(a)-L_(P)(PEG)- orL_(B)′-A_(a)-L_(P)(PEG)- in a Ligand Drug Conjugate or Drug Linkercompound, respectively, when A_(O) is absent.

Typically, secondary linkers with structure (1) are represented by

and secondary linkers with structure (2) are represented by

wherein Y is a self-immolative PAB or PAB-type moeity and E, J/J′, V,Z¹, Z², Z³, R′, R⁸ and R⁹ are as defined in embodiments for PAB orPAB-type self-immolative moieties.

“Maleimide moiety” as used herein is a ligand covalent binding precursormoiety having a maleimide ring system. A maleimide moiety (M¹) as L_(B)′is capable of participating in Michael addition (i.e., 1,4-conjugateaddition) of thiol functional group of a targeting agent to provide athio-substituted succinimide (M²) moiety, as described herein, whichbecomes a component in a Linker Unit in an LDC. An M¹ moiety is attachedto the remainder of the Linker Unit of a Drug Linker compound throughits imide nitrogen prior to its conversion to a thio-substitutedsuccinimide moiety. Other than the imide nitrogen, an M¹ moiety istypically un-substituted, but may be asymmetrically substituted at thecyclic double bond of its maleimide ring system. Such substitutiontypically results in regiochemically preferred addition of a sulfhydrylgroup sulfur atom to the less hindered or more electronically deficientdouble bond carbon (dependent on the more dominant contribution) of themaleimide ring system. When present in a self-stabilizing linker(L_(SS)) moiety of a LDC, controlled hydrolysis of the succinimide ringsystem of the thio-substituted succinimide moiety M² derived from such asubstituted M¹ moiety is expected to or may provide regiochemicalisomers of succinic acid-amide (M³) moieties as L_(B) in aself-stabilized linker (L_(S)) moiety whose relative amount are due todifferences in reactivity of the two carbonyl carbons of M² attributableto the substituent(s) that were present in the M¹ precursor.

“Succinimide moiety” as used herein is an organic moiety of a LinkerUnit of an Ligand Drug Conjugate and results from Michael addition of athiol functional group of a targeting agent to the maleimide ring systemof a maleimide moiety (M¹) as L_(B)′, wherein M¹ is typically that of aDrug Linker compound. In some aspects, the Ligand Drug Conjugate is anAntibody Drug Conjugate and the thiol functional group is from acysteine residue of an antibody or fragment thereof. A succinimide (M²)moiety as L_(B) is therefore comprised of a thio-substituted succinimidering system and has its imide nitrogen substituted with the remainder ofthe Linker Unit and is optionally substituted with substituent(s) thatwere present on the M¹ precursor. Typically, when A is present (i.e.,subscript a of A_(a) is 1) the imide nitrogen is covalently attached tothe Stretcher Unit (A) or subunit thereof (i.e., A₁) as describedherein. Sometimes M²-A (or M²-A₁) provides for a self-stabilizing linker(L_(SS)) moiety as described herein.

“Succinic acid-amide moiety” as used herein refers to succinic acidhaving an amide substituent that results from the thio-substitutedsuccinimide ring system of a succinimide moiety M² as L_(B) havingundergone breakage of one of its carbonyl-nitrogen bonds by hydrolysis.In a ADC hydrolysis resulting in a succinic acid-amide (M³) moietyprovides a Linker Unit less likely to suffer premature loss of itsantibody Ligand Unit having that M³ moiety through elimination of theantibody-thio substituent. When present in a self-stabilizing linker(L_(SS)) moiety, controlled hydrolysis of the succinimide ring system ofthe thio-substituted succinimide moiety M² derived from a substituted M¹moiety as L_(B)′ is expected to provide regiochemical isomers of M³moieties (individually referred to as M^(3A) and M^(3B)) that are due todifferences in reactivity of the two carbonyl carbons of M² attributableto the substituent(s) that were present in the M¹ precursor and thethio-substituent of Ligand Unit, which is from or corresponds to theantibody targeting agent.

“Self-stabilizing linker” as used herein is an L_(B)-containing moietyof Linker Unit of an LDC, or precursor thereof (i.e., aL_(B)′-containing moiety) that under controlled conditions is capable ofundergoing a chemical transformation to a self-stabilized linker(L_(S)), such that an LDC initially comprised of a self-stabilizing(L_(SS)) becomes more resistant to premature loss of its targetingLigand Unit. Usually, a L_(SS) moiety in addition to a L_(B) or L_(B)′moiety is comprised of a first Stretcher Unit (A) to which L_(SS) and-L^(P)(PEG)- are covalently attached. However, sometimes no interveningA is present and L_(SS) is covalently attached directly to -L^(P)(PEG)-.In some aspects, a L_(SS) prior to its incorporation into an LDCcontains a maleimide (M¹) moiety as its L_(B)′ moiety (through which atargeting agent is to be attached as a Ligand Unit) and a firstStretcher Unit (A) or subunit thereof (i.e., A₁) and is represented bythe formula of M¹-A- or M¹-A₁-. After incorporation into an LDC (i.e.,after attachment of the targeting moiety as a Ligand Unit throughMichael addition to the maleimide moiety) the M¹-A- (or M¹-A₁-) moietyof an L_(SS) is converted to its corresponding thio-substitutedsuccinimide moiety M²-A- (or M₂-A₁-). Usually, L_(SS) is also comprisedof a Basic unit (BU) as described herein and is typically a substituentof a Stretcher Unit bound to M² or its M¹ precursor. In those aspects,BU assists in the hydrolysis of the succinimide moiety of M² to itscorresponding ring-opened form M³ [i.e., M²-A(BU)- or M²-A₁(BU)- isconverted to M³-A(BU) or M³-A₁(BU)].

“Self-stabilized linker” is an organic moiety derived from an L_(SS)moiety, both of which are L_(B)-containing moieties, of an LDC that hasundergone hydrolysis, typically under controlled conditions, to providea new L_(B)-containing moiety that is less likely to reverse thecondensation reaction of a targeting agent with a L_(B)′-containingmoiety that provided the original L_(B)-containing moiety. Usually, aself-stabilized linker (L_(S)) is comprised of a Stretcher Unit orsubunit thereof covalently attached to a moiety obtained from conversionof a succinimide moiety (M²) by hydrolysis of its succinimide ringsystem. In those instances, the M² precursor to that moeity has athio-substituted succinimide ring system resulting from Michael additionof a thiol functional group of a targeting agent to the maleimide ringsystem of M¹, so that the M²-derived moiety (M³) has reduced reactivityfor elimination of its thio-substituent in comparison to thecorresponding substituent in M². In those aspects, the M²-derived moietyhas the structure of a succinic acid-amide (M³) moiety corresponding toM² wherein M² has undergone hydrolysis of one of its carbonyl-nitrogenbonds of its succinimide ring system. That hydrolysis may occurspontaneously or more typically is catalyzed by the basic functionalgroup of BU. For that purpose BU is covalently attached to a StretcherUnit bound to M² such that BU is in appropriate proximity as a result ofthat attachment to assist in the rupture of the carbonyl-nitrogen. Theproduct of that hydrolysis therefore has a carboxylic acid functionalgroup and an amide functional group substituted at its amide nitrogenatom, wherein that nitrogen atom corresponds to the imide nitrogen atomin the M²-containing L_(SS) precursor, by the structure of theaforementioned Stretcher Unit. Typically, that basic functional group isan amino group whose effectiveness for increasing the rate of hydrolysisfor the conversion of M² to M³ is controlled by pH. Thus, aself-stabilized linker (L_(S)) typically has the structure of M³covalently bond to a Stretcher Unit or subunit thereof that in turn iscovalently bonded to the remainder of the secondary linker L_(O)(L_(O)′) in a linear arrangement and has a Basic Unit covalently to theStretcher Unit (A) in orthogonal arrangement relative to A and L_(O)′.L_(S) with M³, A, BU and L_(O) arranged in the manner so indicated isrepresented by the formula of M³-A(BU)-L_(O)- or M³-A₁(BU)-L_(O)-.

After hydrolysis, the resulting self-stabilized linker (L_(S)) willtypically have the structure of M³ covalently bond to the BU-substitutedStretcher Unit (e.g., M³-A(Bu)- or M³A₁(BU)-). That first Stretcher Unitin turn is covalently bonded to the remainder of L_(O) in a lineararrangement with the Basic Unit orthogonally arranged with respect to M³and the other L_(O) component units. Exemplary structures of L_(SS) andL_(S) moieties with M² or M³. A(BU) [or A₁(BU)] and L_(O)′-, whereinL_(O)′- represents the remainder of L_(O)-, arranged in the mannerindicated is shown by way of example but not limitation by:

wherein the shown —CH(CH₂NH₂)C(═O)— moiety is the structure of the firstStretcher Unit (A), or subunit thereof, covalently bonded to the imideor amide nitrogen of M² or M³, respectively, wherein the —CH₂NH₂ moietyis the BU substituent of that Stretcher Unit. The remainder of theL_(SS) and L_(S) structures represents the succinimide moiety M² andsuccinic acid-amide moiety M³ from succinimide ring hydrolysis of M²,respectively, wherein M² and M³ are substituted at its imide andcorresponding amide nitrogen, respectively, with a sp³-carbon of theStretcher Unit. The wavy line indicates the point of covalent attachmentto a Ligand Unit resulting from Michael addition of a thiol functionalgroup of a targeting agent to the maleimide ring system of M¹ and theasterisk indicates the point of covalent attachment to D+. Since thesuccinimide ring system of M² is asymmetrically substituted due to itsthio substitution by the Ligand Unit, regiochemical isomers of succinicacid-amide (M³) moieties may be obtained that differ in position of theLigand Unit relative to the liberated carboxylic acid group resultingfrom M² hydrolysis. In the above structures, the carbonyl functionalgroup of the shown Stretcher Unit exemplifies a hydrolysis enhancer (HE)as defined herein that is incorporated into the structure of such aunit.

M³-A(BU)- represents exemplary structures of a self-stabilized linker(L_(S)), since these structures are less likely to eliminate the thiosubstituent of the targeting Ligand Unit, and thus cause loss of thetargeting moeity from its Ligand Drug Conjugate, in comparison to thecorresponding M²-A(BU)- structure of an L_(SS) moiety. Without beingbound by theory, that increased stability is believed to result from thegreater conformational flexibility in M³ in comparison to M², which nolonger constrains the thio substituent in a conformation favorable forE2 elimination.

“Basic Unit” as used herein is an organic moiety within aself-stabilizing linker (L_(SS)), as described herein, that can becarried forward into a corresponding L_(S) by effecting hydrolysis ofthe succinimide ring system within a M² moiety comprising L_(SS) (i.e.,catalyzes water addition of a water molecule to one of the succinimidecarbonyl-nitrogen bonds) and can be initiated or enhanced undercontrolled conditions tolerable by the targeting Ligand Unit attached toL_(SS). For that purpose, the basic functional group of the Basic Unit(BU) and its relative position in L_(SS) with respect to its M²component in some aspects is selected for its ability to hydrogen bondto a carbonyl group of M², which effectively increases itselectrophilicity and hence its susceptibility to water attack. Inanother aspect, those selections are made so that a water molecule,whose nucleophilicity is increased by hydrogen bonding to the basicfunctional group of BU, is directed to an M² carbonyl group. In a thirdaspect, those selections are made so the basic nitrogen on protonationincreases the electrophilicity of the succinimide carbonyls by inductiveelectron withdrawing. In a final aspect, some combination of thosemechanisms contributes to catalysis for hydrolysis of L_(SS) to L_(S).

For increasing the electrophilicity of an M² carbonyl by hydrogenbonding, BU is required to have a primary or secondary amine as itsbasic functional group whereas increasing water nucleophilicity orcarbonyl electrophilicity in the manner described above may be done witha primary, secondary or tertiary amine as the basic functional group. Inorder that a basic amine be in the required proximity to assist in thehydrolysis of a succinimide moiety M² to its corresponding ring openedcarboxylic acid amide M³ by any one of those mechanisms, theamine-bearing carbon chain of BU is typically attached to a StretcherUnit of L_(SS) at the alpha carbon of that moiety relative to the pointof attachment of A (or A₁) to the succinimide nitrogen of M² (and henceto the maleimide nitrogen of its corresponding precursor M¹-A or M¹-A₁structure). In some aspects, that alpha carbon has the (S)stereochemical configuration or the configuration corresponding to thatof the alpha carbon of L-amino acids.

“Hydrolysis Enhancer Unit” as used herein is electron withdrawing groupor moiety and is an optional substituent of a Stretcher Unit comprisingan L_(SS) moiety. When present, a Hydrolysis Enhancer Unit (HE) isusually incorporated into a Stretcher Unit that is bonded to the imidenitrogen of an M² moiety so that its electron withdrawing effectsincreases the electrophilicity of the succinimide carbonyl groups inthat moiety. When the Stretcher Unit also has a BU substituent, theeffect of HE on the carbonyl groups coupled with the effect of BU, whichis dependent on the basicity of the BU basic functional group and thedistance of that functional group in relation to those carbonyl, arebalanced so that premature hydrolysis of M¹ or of M² to M³ does notoccur to an appreciable extent that would require an excessive excess ofa Drug Linker compound for the preparation of an LDC from an L_(SS)precursor having the structure of M¹-A(BU)-, but allows for hydrolysis(i.e., conversion of an LDC-containing -M²-A(BU)- moiety to itscorresponding -M³-A(BU)- moiety) under controlled conditions (as when pHis purposely increased) that are tolerable by the attached targetingLigand Unit. Typically, the HE Unit is a carbonyl or carbonyl-containingfunctional group located distal to the end of the Stretcher Unit that isbonded to M², or M³ derived therefrom, so that HE is covalently attachedto that stretcher unit and to the remainder of the secondary linker.Carbonyl-containing functional groups other than ketone (i.e. HE is—C(═O)—) include esters, carbamates, carbonates and ureas. When HE is acarbonyl-containing functional group other than ketone the carbonylmoiety of that functional group is typically bonded to A. In someaspects, the HE Unit may be sufficiently distant within a Stretcher Unitfrom the imide nitrogen to which the stretcher unit is covalently bondedso that no discernable effect on hydrolytic sensitivity of thesuccinimide carbonyl-nitrogen bonds of an M²-containing moiety isobservable.

“Stretcher Unit” as the term is used herein refers to an organic moietyin a secondary linker that physically separates the targeting moietyfrom other intervening components of a Linker unit that are distal tothe stretcher unit, such as a cleavable unit and/or a spacer unit. Afirst Stretcher Unit (A) and/or second Stretcher Unit (A_(O)) may berequired when a L_(B) and/or a -L^(P)(PEG)- moiety provides insufficientsteric relief to allow for efficient processing of the Linker Unit at Wor W′ for release of D⁺ as a tubulysin drug and/or is sometime includedfor synthetic ease in constructing a Linker Unit of the presentinvention. A first or second Stretcher unit can comprise one or multiplestretcher subunits as described herein. Prior to incorporation into anLDC, A has functional groups capable of covalently binding L_(B)′ to-L^(P)(PEG)-, and A_(O) has functional groups capable of covalentlybinding -L^(P)(PEG)- and a Cleavable unit (W) together in certain linkerconstructs (as with A, W and Y in a linear arrangement, i.e., -A-Y—W—)or A_(O) has functional groups capable of covalently binding-L^(P)(PEG)- and a Spacer unit (Y) together in other linker constructs(as with W′ orthogonal to A and Y, i.e., -A-Y(W′)—). In some aspects ofthe invention, the secondary linker is attached to a L_(B) or L_(B)′moiety through a subunit of a first Stretcher Unit while another of itssubunits is covalently bonded to -L^(P)(PEG)-.

A first Stretcher unit (A), when present in an LDC or Drug Linkercompound, are typically in Linker Units having the formula of-A-L^(P)(PEG)-W—Y—, -A-L^(P)(PEG)-A_(O)-W—Y—, A-L^(P)(PEG)-Y(W′)— orA-L^(P)(PEG)-A_(O)-Y(W′)— in which A is attached to a Ligand CovalentBinding Unit or a Ligand Covalent Binding Unit precursor. A first orsecond Stretcher Unit may comprise or consist of two, three or moresubunits. Typically, A is one distinct unit or has 2 to 4 additionaldistinct subunits referred to as A₂, A₃ and A₄. In those A₃ is -A₁-A₂,-A₁-A₂-A₃-, and -A₁-A₂-A₃-A₄-, collectively described as -A₁-A₂₋₄-.Typically, a First Stretcher Unit or a subunit thereof has one to sixcontiguous carbon atoms that are between a Ligand Covalent Binding Unitor a Ligand Covalent Binding Unit precursor and a functional group thatcovalently attaches A to -L^(P)(PEG)- or to another subunit of A. Insome aspects that functional group may also serve as a hydrolysisenhancing (HE) unit.

“Branching Unit” as used herein refers to an tri-functional organicmoiety that is an optional component of a Linker Unit (LU). A BranchingUnit (B) is present when more than one quaternary tubulysin Drug Unit(D), typically 2, 3 or 4, are attached to a Linker Unit (LU) of a LigandDrug Conjugate or Drug Linker compound. In a Ligand Drug Conjugate ofFormula 1A, 1B, 1C or 1D or a Drug Linker compound of Formula IA, IB or1D, the presence of a Branching Unit is indicated when subscript b ofB_(b) is 1, and occurs when subscript n greater than 1 in either one ofthese structural formulae. A Branching Unit is trifunctional in order tobe incorporated into a secondary linker unit (L_(O)). In aspects where nis 1 in either of those structural formulae, a Branching Unit is eithernot present, as indicated when subscript b is 0 or subscript b is 1 andB is replaced by second optional Stretcher Unit designated as A_(O). ADrug Linker compound or Ligand Drug Conjugate having a Branching Unitdue to multiple D⁺ units per LU have Linker Units comprised of moietiessuch as -A_(a)-L^(P)(PEG)-B—W—Y— or -A_(a)-L^(P)(PEG)-B—Y(W′)—.

In some aspects a natural or un-natural amino acid or otheramine-containing acid compound having a functionalized side chain servesas a Branching unit. In some aspects B is a lysine, glutamic acid oraspartic acid moiety in the L- or D-configuration in which theepsilon-amino, gamma-carboxylic acid or beta-carboxylic acid functionalgroup, respectively, interconnects B to the remainder of LU.

“Cleavable Unit” as defined provides for a reactive site in whichreactivity to that site is greater within or surrounding ahyper-proliferating cell or a hyper-stimulated immune cell (i.e., anabnormal cell) in comparison to a normal cell such that action upon thatsite results in preferential exposure to the abnormal cell to tubulysindrug (D). That exposure results from eventual release of a quaternizedtubulysin Drug Unit (D⁺) as D from an LDC having that Cleavable Unit. Insome aspects of the invention, a Cleavable Unit, W or W′ is comprised ofa reactive site cleavable by an enzyme (i.e., W or W′ is comprised of anenzyme substrate) whose activity or abundance is greater within orsurrounding the hyper-proliferating, immune-stimulating or otherabnormal or unwanted cell. In other aspects, a Cleavable Unit iscomprised of a reactive site cleavable by other mechanisms (i.e.,non-enzymatic) more likely operable in the environment within orsurrounding abnormal cells of the target site in comparison to theenvironment of normal cells in which abnormal cells are typically notpresent. In still other aspects of the invention, the reactive site ismore likely operated upon subsequent to cellular internalization of theLDC into an abnormal cell. That internalization more likely occurs inthose cells in comparison to normal cells due to greater presentation ofthe targeted moiety that is recognized by the targeting Ligand Unit ofthe LDC on the cellular membrane of the abnormal or unwanted cells.Therefore, the targeted cells will more likely be exposedintracellularly to an active drug moiety when liberated from its LDC.The Cleavable Unit can comprise one or multiple sites susceptible tocleavage under those conditions of the targeted site, but typically hasonly one such site.

In some aspects of the invention, the Cleavable Unit is a substrate fora regulatory protease, hydrolase or glycosidase located intracellularlyin the targeted cells (i.e., the reactive site of W or W′ is a peptidebond or glycoside bond, respectively, cleavable by the regulatoryprotease, hydrolase or glycosidase). In those aspects the peptide orglycoside bond is capable of selective cleavage by the regulatoryprotease, hydrolase or glycosidase in comparison to serum proteases,hydrolases, or glycosidases. Those regulatory proteases, hydrolases orglycosidases may be more specific to the targeted abnormal or otherunwanted cells in comparison to normal cells, or W or W′ is capable ofselective cleavage by a protease, hydrolase or glycosidase excreted ingreater amounts by the targeted abnormal or other unwanted cells incomparison to normal cells or by targeted normal cells that are peculiarto the environment of the abnormal cells in comparison to normal cellsin the periphery. Alternatively, W provides for a functional group thatwhen incorporated into an LDC is susceptible to the acidic environmentof lysozymes when the LDC is preferentially internalized into anabnormal cell, or to the greater reductive environment in or aroundthese cells in comparison to the environment of normal cells whereabnormal cells usually are not present such that release of D⁺ as atubulysin drug preferentially exposes the abnormal cells to that drug incomparison to normal cells distant from the site of the abnormal cells.

The Cleavable unit (W or W′), in a Drug Linker compound or after itsincorporation into an LDC, provides for a cleavable bond (i.e., areactive site) that in some aspects upon action by an enzyme presentwithin a hyper-proliferating cell or hyper-activated immune cellsreleases a tertiary amine-containing drug from D⁺. In other aspects, thereleasing enzyme is characteristic of the immediate environment of thoseabnormal or unwanted cells. In still other aspects non-enzymatic actionon W due to conditions more likely experienced by hyper-proliferatingcells in comparison to normal cells will release free tubulysin drugfrom D⁺. Typically, W or W′ provides for a cleavable bond that is morelikely acted upon intracellularly in a hyper-proliferating cell orhyper-activated immune cell due to preferential entry into such cells incomparison to normal cells. Typically, W or W′ in an LDC or Drug Linkercompound is covalently attached to a Spacer Unit (Y) having aself-immolating moiety such that enzymatic action on W or W′ triggersself-destruction of that moiety within —Y-D⁺ of —W—Y-D⁺ or —Y(W′)-D⁺,respectively, to release D⁺ as D.

Functional groups that provide for cleavable bonds include, by way ofexample and not limitation, (a) sulfhydryl groups that form a disulfidebond, which are more susceptible to the greater reductive conditions ofabnormal cells in comparison to normal cells or excess glutathioneproduced under hypoxic conditions experienced by such cells, (b)aldehyde, ketone, or hydrazine groups that form a Schiff base orhydrazone functional groups, which are more susceptible to the acidicconditions of lysozymes upon selective internalization of an LDC havinga Linker Unit with that cleavable bond into an abnormal cell incomparison to its internalization into normal cells, (c) carboxylic oramino groups that form an amide bond, as in peptide bonds, that are moresusceptible to enzymatic cleavage by proteases produced or excretedpreferentially by abnormal cells in comparison to normal cells, orpreferentially excreted by normal cells that are peculiar to theenvironment of abnormal cells in comparison to normal cells in theperiphery, or by a regulatory protease within a targeted cell, (d) aminoor hydroxyl groups that form certain urea or carbamate groups orcarboxylic or hydroxy groups that form ester or carbonate groups thatare more susceptible to enzymatic cleavage by hydrolases or esterasesthat are produced or excreted preferentially by abnormal cells incomparison to normal cells or are excreted preferentially be normalcells peculiar to the environment of abnormal cells in comparison tonormal cells in the periphery.

Still other functional groups that provide for cleavable bonds are foundin sugars or carbohydrates having a glycosidic linkage that aresubstrates for glycosides which sometimes may be produced preferentiallyby abnormal cells in comparison to normal cells. Alternatively, theprotease, hydrolase or glycosidase enzyme required for processing of theLinker Unit to release D⁺ as an active tubulysin drug need not beproduced preferentially by abnormal cells in comparison to normal cellsprovided the processing enzyme is not excreted by normal cells to anentent that would cause undesired side effects from premature release offree drug. In other instances the required protease, hydrolase orglycosidase enzyme may be excreted but to avoid undesired prematurerelease of drug, it is preferred that the processing enzyme be excretedin the vicinity of abnormal cells and remain localized to thatenvironment, whether produced by abnormal cells or nearby normal cellsin response to the abnormal environment caused by the abnormal cells. Inthat respect W or W′ is selected to be preferentially acted upon by aprotease, hydrolase or glycosidase in or within the environment ofabnormal cells in contrast to freely circulating enzymes. In thoseinstances, a LDC is less likely to release the tubulysin drug in thevicinity of normal cells distant from the desired site of action norwould it be internalized into normal cells that do produce but notexcrete the selected enzyme since such cells are less likely to displaya targeted moiety required for entry by the LDC through selectivebinding by its targeting Ligand Unit.

In some aspects. W is a Peptide Cleavable Unit comprised of an aminoacid or is comprised or consists of one or more sequences of amino acidsthat provide a substrate for a protease present within abnormal cells orlocalized to the environment of these abnormal cells. Thus, W may becomprised or consist of a dipeptide, tripeptide, tetrapeptide,pentapeptide, hexapeptide, heptapeptide, octapeptide, nonapeptide,decapeptide, undecapeptide or dodecapeptide moiety incorporated into aLinker Unit through an amide bond to a self-immolative Y wherein thatpeptide moiety is a recognition sequence for that protease. In someaspects W is a single natural L-amino acid, such as L-glutamate.

In some aspects, W′ of a Glucuronide Unit of formula —Y(W′)— iscomprised or consists of a carbohydrate moiety attached to aself-immolative moiety of Y by a glycosidic bond that is cleavable by aglycosidase preferentially produced by abnormal cells, or is found insuch cells to which an LDC, which is comprised of that self-immolativeand carbohydrate moieties, has selective entry due to the presence ofthe targeted moiety on the abnormal cells.

“Spacer Unit” as used herein is an organic moiety in a secondary linker(L_(O)) within a Linker Unit that is covalently bonded to D⁺ and asecond optional Stretcher Unit (A_(O)) or a Branching Unit (B), ifeither is present, or to -L^(P)(PEG)- if A_(O) And B are absent and/orto a cleavable unit (W or W′) depending on the configuration of theCleavable Unit to the Spacer Unit relative to each other. Typically, inone configuration, a quaternized drug unit (D⁺) and W′ are bothcovalently bonded to Y which in turn is also bonded to A_(O) or B, wheneither is present, or to L^(P)(PEG) when both are absent so that W′ isorthogonal to the remainder of L_(O), whereas in another configurationW, Y. D⁺ are arranged in a linear configuration with D⁺ bonded to Y. Ineither arrangement, Y may also serve to separate the cleavage site of Wor W′ from D⁺ to avoid steric interactions from that unit that wouldinterfere with cleavage of W/W′ whenever that cleavage is preformedthrough enzymatic action.

Typically, a Spacer Unit (Y) having a self-immolating moiety as definedherein has that moiety covalently bonded to a cleavage unit (W/W′) sothat in vivo processing of the Cleavable Unit activates self-destructionof Y thus a tubulysin drug from D⁺. In some aspects the self-immolativemoiety of Y is bonded to W through a amide (or anilide) functional groupwith Y also covalently bonded to the quaternary amine nitrogen of D⁺ sothat spontaneous self-destruction of the self-immolative moeity occursupon enzymatic action on that functional group to result in release offree tubulysin drug from D⁺. In other aspects the self-immolative moeityof Y is attached to W′ through a glycosidic bond so that cleavage ofthat bond releases free tubulysin drug from D⁺.

“Self-immolating moiety” as used herein refers to a bifunctional moietywithin a spacer unit (Y) having an organic moiety that intervenesbetween the first and second functional group moieties and covalentlyincorporates these moieties into a normally stable tripartite moleculeunless activated. On activation when the covalent bond to the firstfunctional group moiety is cleaved, the second functional group moietyspontaneously separates from the tripartite molecule by self-destructionof the remainder of the self-immolative moiety. That self-destruction onactivation releases free tubulysin drug (D). In some aspects thatself-destruction occurs after cellular internalization of an LDCcomprising D⁺ and a Linker Unit having a self-immolating Spacer Unit.The intervening organic moiety in between the functional group moietiesof a self-immolating moiety is sometimes an arylene or heteroarylenemoiety capable of undergoing fragmentation to form a quinone methide orrelated structure by 1,4 or 1,6-elimination with concomitant release offree tubulysin drug. Such self-immolative moieties are exemplified byoptionally substituted p-aminobenzyl alcohol (PAB) moieties, ortho orpara-aminobenzylacetals, or aromatic compounds that are electronicallysimilar to the PAB group (i.e., PAB-type) such as2-aminoimidazol-5-methanol derivatives (see, e.g., Hay et al., 1999.Boorg. Med. Chem. Lett. 9:2237) and other heteroaryls as describedherein.

In one aspect, an aromatic carbon of an arylene or heteroarylene groupof a PAB or PAB-type self-immolative moiety when incorporated into aLinker Unit is substituted with an electron-donating (EDG) heteroatomattached to the cleavage site of W through a first functional groupcomprising the heteroatom wherein that heteroatom is functionalized sothat its electron-donating capacity is attenuated (i.e., the EDG ismasked by incorporation of the self-immolative moeity of Y into a Linkerunit). The other substituent that provides the second functional groupis a benzylic carbon that is also attached to another aromatic carbonatom of the central arylene or heteroarylene group and has a quaternaryamine substituent, in which the quaternary amine corresponds to orincorporates a tubulysin drug, is bonded through the benzylic carbon,wherein the aromatic carbon bearing the attenuated electron-donatingheteroatom is adjacent to (i.e., 1,2-relationship), or two additionalpositions removed (i.e., 1,4-relationship) from that benzylic carbonatom. The EDG is chosen so that processing of the cleavage site of Wrestores the electron-donating capacity of the masked EDG thustriggering a 1,4- or 1,6-elimination to expel the tubulysin drug fromthe benzylic quaternary amine substituent.

Exemplary -L_(O)-D⁺ moieties having PAB or PAB-related self-immolativemoieties containing a central arylene or heteroarylene with therequisite 1,2- or 1,4-substitution patterns that allow for 1,4- or1,6-fragmentation to release D from a quaternized Drug Unit arerepresented by:

wherein D⁺ in —C(R⁸)(R⁹)-D⁺ is covalently attached to the aforementionedbenzylic carbon through a quaternary amine nitrogen that correspondingto the tertiary amine nitrogen of a tubulysin drug (D) to be releasedfrom D⁺, and J is the heteroatom, which is bonded to W through theaforementioned attenuating functional group comprising J and isoptionally substituted if nitrogen (i.e., J is optionally substituted—NH), wherein J is —O—, —N(R³³)—, or —S—, and R⁸, R⁹, R³³, R′, V, Z¹,Z², Z³ are defined in embodiments of self-immolative Spacer Unitscontaining PAB or PAB-type moieties. Those variables are selected sothat reactivity of J when released from processing of W at the targetedsite is appropriately balanced with the reactivity of the tertiary amineof the tubulysin drug eliminated from the self-immolative moeity of Yand the stability of the quinone-methide type intermediate resultingfrom that elimination for effective release of D⁺ as D.

In some aspects for a -L_(O)-D⁺ moiety of structure (2), the Spacer Unitof L_(O) having a PAB or PAB-type self-immolative moiety bound to D⁺ hasthe structure of:

wherein the wavy line to J′ indicates stable covalent bonding (i.e., notprocessed at the targeted site) to Ligand-L_(B)-A-L^(P)(PEG)-A_(O)- in aLigand Drug Conjugate, or L_(B)′-A-L^(P)(PEG)-A_(O)- in a Drug Linkercompound when a is 1 and A_(O) is optionally present, or toLigand-L_(B)-Aa-L^(P)(PEG)-B— or L_(B)*-A_(a)-L^(P)(PEG)-B—, wherein ais 0 or 1 and wherein J′ is —O—, —N(R³³)—, or —S— bonded directly toA_(O), B or a subunit thereof, or to Ligand-L_(B)-L^(P)(PEG)-, orL_(B)′-L^(P)(PEG)- when none of A, B and A_(O) is present, through afunctional group comprising J′, and wherein R′, R⁸, R⁹, V, Z¹, Z² and Z³are as defined in Formula 1A or Formula IA and E′, independentlyselected from J′, is an electron donating group from W′ such as —O—,—N(R³³)—, or —S—, wherein R³³ is —H, optionally substituted alkyl oroptionally substituted aralkyl and the electron donating ability of E′is attenuated by its bonding to the carbohydrate moeity of W′, whereinthe W′-E′ bond provides for a cleavage site for a glycosidase, and E′and the benzylic carbon of the —C(R⁸)(R⁹)-D⁺ moiety are bonded to theaforementioned central arylene or heteroarylene at positions defined byV, Z¹, Z² or Z³, such that E′ and the —C(R⁸)(R⁹)-D⁺ moiety are in a 1,2or 1,4 relationship so as to permit the 1,4- or 1,6-fragmentation thatresults in release of D⁺ as a tubulysin drug.

In some aspects for a -L_(O)-D⁺ moiety of structure (1), the Spacer Unitof 1, having a PAB or PAB-type self-immolative moiety bound to D⁺ hasthe structure of:

wherein R′, R⁸, R⁹, V, Z¹ and Z² are as defined in Formula 1D or FormulaID, R³³ is —H, optionally substituted alkyl or optionally substitutedaralkyl and the waving line adjacent to the optionally substitutednitrogen heteroatom indicates the site of covalent bonding to W to theremainder of L_(O) wherein W is bonded toLigand-L_(B)-A-L^(P)(PEG)-A_(O)-, in a Ligand Drug Conjugate or toL_(B)′-A-L^(P)(PEG)-A_(O)- in a Drug Linker compound when subscript a is1 and A_(O) is optionally present, or toLigand-L_(B)-A_(a)-L^(P)(PEG)-B— or L_(B)′-A_(a)-L^(P)(PEG)-B— whereinsubscript a is 0 or 1, or to Ligand-L_(B)-L^(P)(PEG)-, orL_(B)′-L^(P)(PEG)-when none of A, B and A_(O) is present, whereinselective protease action at that covalent is bond initiatesself-immolation of the Spacer Unit to release D⁺ as D.

In some aspects for a -L_(O)-D⁺ moiety of structure (2), the Spacer Unitof L_(O) having a PAB or PAB-type self-immolative moiety bound to D⁺ hasthe structure of

wherein E′, J′, R′, R⁸, R⁹, V, and Z³ are as defined in Formula 1A orFormula IA. Other structures and their variable group definitionsincorporating an self-immolative moiety in a secondary linker-D⁺ moietyof structure (2) are provided by the embodiments.

The arylene or heteroarylene of an self immolative moiety of Y may befurther substituted to affect the kinetics of the 1,2- or1,4-elimination in order to modulate the release of D⁺ as D or toimprove the physiochemical properties of the Ligand Drug Conjugate(e.g., reduce hydrophobicity) into which it is incorporated. Forexample, other than hydrogen R′ can be an electron withdrawing groupsuch as chloro, fluoro, or —NO₂, as when E′ is an oxygen atom of aglycosidic bond to the carbohydrate moeity of W′.

Other exemplary and non-limiting examples of self-immolative structuresthat can be modified to accommodate benzylic quaternary aminesubstituents are provided by Blencowe et al. “Self-immolative linkers inpolymeric delivery systems” Polym. Chem. (2011) 2: 773-790; Greenwald etal. “Drug delivery systems employing 1,4- or 1,6-elimination:poly(ethylene glycol) prodrugs of amine-containing compounds” J. Med.Chem. (1999) 42: 3657-3667; and in U.S. Pat. Nos. 7,091,186; 7,754,681;7,553,816; and 7,989,434, all of which are incorporated by referenceherein in their entireties with the structures and variable groupsprovided therein specifically incorporated by reference.

“Cytotoxic drug” as used herein refers to compound or a metabolitederived from an LDC that exerts an anti-survival effect onhyper-proliferating cells, hyper-activated immune cells or otherabnormal or unwanted cells. In some aspects the cytotoxic drug actsdirectly upon those cells or indirectly by acting upon the abnormalvasculature that supports the survival and/or growth of thehyper-proliferating or other abnormal or unwanted cells, or thecytotoxic drug acts within sites of infiltrating hyper-activated immunecells. Typically, the abnormal or unwanted cells acted upon by thecytotoxic drug are mammalian cells, more typically human cells.Cytotoxic activity of a cytotoxic drug may be expressed as an IC₅₀value, which is the effective concentration, typically molar amount perunit volume, at which half the cancer cells in an in vitro cell modelsystem survive exposure to the cytotoxic agent. Thus, an IC₅₀ value ismodel-dependent. Typically, a cytotoxic agent incorporated into an LDCwill have an IC₅₀ value in an in vitro cell model comprised ofhyper-proliferating cells of between 100 nM to 0.1 μM or more typicallyabout 10 nM to 1 pM. A highly toxic cytotoxic drug typically has an IC₅₀value in such models of about 100 pM or lower. Although multiple drugresistant inhibitors that reverse resistance to cytotoxic drugs are notcytotoxic in their own right they are sometimes included as cytotoxicdrugs. In some instances, a cytotoxic drug for use in the presentinvention is a cytotoxic tubulysin compound containing a tertiary aminenitrogen that can be quaternized for incorporation as D⁺ into astructure representing Ligand Drug Conjugate composition. In otherinstances a cytotoxic tubulysin drug compound having a tertiary amineresults when D⁺ is released as D from a Ligand Drug Conjugate compoundin a composition of the present invention.

“Cytostatic drug” as used herein refers to compound or a metabolitederived from an LDC that exerts an inhibitory effect on the growth andproliferation of hyper-proliferating cells, hyper-activated immune cellsor other abnormal or unwanted cells. In some aspects the cytostatic drugacts directly upon those cells or indirectly by acting upon the abnormalvasculature that supports the survival and/or growth of thehyper-proliferating or other abnormal or unwanted cells, or thecytotoxic drug acts within sites of infiltrating hyper-activated immunecells. Typically, the abnormal or unwanted cells acted upon by thecytotoxic drug are mammalian cells, more typically human cells. Althoughmultiple drug resistant inhibitors that reverse resistance to cytostaticdrugs are not cytostatic in their own right they are sometimes includedas cytostatic drugs. In some instances, a cytostatic drug for use in thepresent invention is a cytostatic tubulysin compound containing atertiary amine nitrogen that can be quaternized for incorporation as D⁺into a structure representing Ligand Drug Conjugate composition. Inother instances a tubulysin compound that is cytostatic and having atertiary amine nitrogen results when D⁺ is released as D from a LigandDrug Conjugate compound in a composition of the present invention.

“Hematological malignancy” as the term is used herein refers to a bloodcell tumor that originates from cells of lymphoid or myeloid origin andis synonymous with the term “liquid tumor”. Hematological malignanciesmay be categorized as indolent, moderately aggressive or highlyaggressive.

“Lymphoma” as used herein is hematological malignancy that usuallydevelops from hyper-proliferating cells of lymphoid origin. Lymphomasare sometimes classified into two major types: Hodgkin lymphoma (HL) andnon-Hodgkin lymphoma (NHL). Lymphomas may also be classified accordingto the normal cell type that most resemble the cancer cells inaccordance with phenotypic, molecular or cytogenic markers. Lymphomasubtypes under that classification include without limitation matureB-cell neoplasms, mature T cell and natural killer (NK) cell neoplasms,Hodgkin lymphoma and immunodeficiency-associated lympho-proliferativedisorders. Lymphoma subtypes include precursor T-cell lymphoblasticlymphoma (sometimes referred to as a lymphoblastic leukemia since theT-cell lymphoblasts are produced in the bone marrow), follicularlymphoma, diffuse large B cell lymphoma, mantle cell lymphoma, B-cellchronic lymphocytic lymphoma (sometimes referred to as a leukemia due toperipheral blood involvement), MALT lymphoma, Burkitt's lymphoma,mycosis fungoides and its more aggressive variant Sézary's disease,peripheral T-cell lymphomas not otherwise specified, nodular sclerosisof Hodgkin lymphoma, and mixed-cellularity subtype of Hodgkin lymphoma.

“Leukemia” as the term is used herein is a hematological malignancy thatusually develops from hyper-proliferating cells of myeloid origin, andinclude without limitation, acute lymphoblastic leukemia (ALL), acutemyelogenous leukemia (AML), chronic lymphocytic leukemia (CLL), chronicmyelogenous leukemia (CML) and acute monocyctic leukemia (AMoL). Otherleukemias include hairy cell leukemia (HCL), T-cell lymphatic leukemia(T-PLL), large granular lymphocytic leukemia and adult T-cell leukemia.

“Quaternized Drug Unit” or quaternized tubulysin Drug Unit as usedherein is an incorporated tertiary amine-containing tubulysin compound(D) or corresponds to such a compound in which the tertiary aminenitrogen is present in the compound structure as quaternary amine saltand exhibits cytotoxic, cytostatic, immunosuppressive oranti-inflammatory property, typically against mammalian cells, whenreleased from a Ligand Drug Conjugate compound. In some aspects, aquaternized tubulysin Drug Unit (D⁺) is obtained by condensing thetertiary amine nitrogen of the C-terminal component of a tubulysincompound with a secondary linker L_(O) precursor having a suitableleaving group. In some aspects the tertiary amine-containing tubulysincompound is converted to its quaternized form upon its incorporationinto a L_(B) or L_(B)′-containing moiety. In other aspects theC-terminal component is first quaternized with the remainder of thetubulysin then appended to complete the D⁺ Unit. Therefore, structuressuch as L-L_(B)-L_(O)-D⁺ and L_(B)′-L_(O)-D⁺ imply no particular methodin which D⁺ was formed and does not require that a reactant used in itsformation be a tertiary-amine containing drug, but only require D⁺ toincorporate or correspond to the structure of the tertiary-aminecontaining intended to be released from a Ligand Drug Conjugatecompound. The class of tertiary-amine containing drugs released from anLDC of the present invention encompasses tubulysin compounds asdescribed herein having cytotoxic or cytostatic effects on abnormal orother unwanted cells.

“Hyper-proliferating cells” as used herein refers to cells that arecharacterized by unwanted cellular proliferation or an abnormally highrate or persistent state of cell division that is unrelated oruncoordinated with that of the surrounding normal tissues. Typically,the hyper-proliferating cells are mammalian cells. In some aspects thehyper-proliferating cells are hyper-stimulated immune cells as definedherein whose persistent state of cell division occurs after thecessation of the stimulus that may have initially evoked the change intheir cell division. In other aspects the hyper-proliferating cells aretransformed normal cells or cancer cells and their uncontrolled andprogressive state of cell proliferation may result in a tumor that isbenign, potentially malignant (premalignant) or frankly malignant.Hyperproliferation conditions resulting from transformed normal cells orcancer cells include but are not limited to those characterized as aprecancer, hyperplasia, dysplasia, adenoma, sarcoma, blastoma,carcinoma, lymphoma, leukemia or papilloma. Precancers are usuallydefined as lesions that exhibit histological changes which areassociated with an increased risk of cancer development and sometimeshave some, but not all, of the molecular and phenotypic properties thatcharacterize the cancer. Hormone associated or hormone sensitiveprecancers include, prostatic intraepithelial neoplasia (PIN),particularly high-grade PIN (HGPIN), atypical small acinar proliferation(ASAP), cervical dysplasia and ductal carcinoma in situ. Hyperplasiasgenerally refers to the proliferation of cells within an organ or tissuebeyond that which is ordinarily seen that may result in the grossenlargement of an organ or in the formation of a benign tumor or growth.Hyperplasias include, but are not limited to endometrial hyperplasia(endometriosis), benign prostatic hyperplasia and ductal hyperplasia.

“Normal cells” as used herein refers to cells undergoing coordinatedcell division related to maintenance of cellular integrity of normaltissue or replenishment of circulating lymphatic or blood cells that isrequired by regulated cellular turnover, or tissue repair necessitatedby injury, or to a regulated immune or inflammatory response resultingfrom pathogen exposure or other cellular insult, where the provoked celldivision or immune response terminates on completion of the necessarymaintenance, replenishment or pathogen clearance. Normal cells includenormally proliferating cells, normal quiescent cells and normallyactivated immune cells.

“Normal quiescent cells” are noncancerous cells in their resting G_(o)state and have not been stimulated by stress or a mitogen or are immunecells that are normally inactive or have not been activated bypro-inflammatory cytokine exposure.

“Hyper-stimulated immune cells” as the term is used herein refers tocells involved in innate or adaptive immunity characterized by anabnormally persistent proliferation or inappropriate state ofstimulation that occurs after the cessation of the stimulus that mayhave initially evoked the change in proliferation or stimulation or thatoccurs in the absence of any external insult. Oftentimes, the persistentproliferation or inappropriate state of stimulation results in a chronicstate of inflammation characteristic of a disease state or condition. Insome instance the stimulus that may have initially evoked the change inproliferation or stimulation is not attributable to an external insultbut is internally derived as in an autoimmune disease. In some aspects ahyper-stimulated immune cells is a pro-inflammatory immune cell that hasbeen hyper-activated through chronic pro-inflammatory cytokine exposure.

In some aspects of the invention an LDC binds to an antigenpreferentially displayed by pro-inflammatory immune cells that areabnormally proliferating or are inappropriately activated. Those immunecells include classically activated macrophages or Type 1 T helper (Th1)cells, which produce interferon-gamma (INF-γ), interleukin-2 (IL-2),interleukin-10 (IL-10), and tumor necrosis factor-beta (TNF-β), whichare cytokines that are involved in macrophage and CD8⁺ T cellactivation.

“Glycosidase” as used herein refers to a protein capable of enzymaticcleavage of a glycosidic bond. Typically, the glycosidic bond to becleaved is present in a Cleavable unit (W′) of an LDC. Sometimes theglycosidase acting upon an LDC is present intracellularly inhyper-proliferating cells, hyper-activated immune cells or otherabnormal or unwanted cells to which the LDC has preferential access incomparison to normal cells, which is attributable to the targetingcapability of the ligand-binding component (i.e., the Ligand Unit).Sometimes the glycoside is more specific to the abnormal or unwantedcells or is preferentially excreted by abnormal or unwanted cells incomparison to normal cells or is present in greater amount in thevicinity of abnormal or unwanted in comparison to serum amounts.Oftentimes the glycosidic bond in W′ acted upon by a glycosidaseattaches the anomeric carbon of a carbohydrate moiety (Su) to a phenolicoxygen of a self-immolating (SI) moiety that comprises a self-immolativeSpacer Unit (Y) such that glycosidic cleavage of that bond triggers 1,4-or 1,6-elimination of an tertiary amine-containing tubulysin drug fromthe quaternary amine moiety bonded to the benzylic position of SI.

In some aspects, Drug Linker compounds or Ligand Drug Conjugates arecomprised of moieties such as -A_(a)-L_(P)(PEG)-B_(b)—Y(W′)-D⁺ or-A_(a)-L_(P)(PEG)-A_(O)-Y(W′)-D⁺, in which the subscripts a and b areindependently 0 or 1, wherein the —Y(W′)— moiety is typically a Su-O′—moiety bonded to a self-immolative moeity of Y as defined herein withA_(O) or -L_(P)(PEG)-, W′ and D⁺ attached to the self-immolative moeityin a manner that permits self-immolative release of free tertiary aminecontaining tubulysin compound upon action by a glycosidase. Such —Y(W′)—moieties are sometimes referred to as a Glucuronide Unit in which Su isa carbohydrate moeity, which is not limited to that of a glucuronicacid.

Typically, a Su-O′— moiety (where —O′— represents the oxygen of theglycosidic bond and Su is a carbohydrate moiety) bonded to aself-immolative moeity of Y is represented by the structure describedfor self-immolating moieties wherein E′ bonded to the central arylene orheteroarylene of the self-immolative moeity is oxygen and wherein thatheteroatom is substituted with a carbohydrate moiety through itsanomeric carbon atom. More typically Su-O′—Y-D⁺ has the structure of:

wherein R^(24A), R^(24B) and R^(24C), is as defined for R²⁴ in thesummary of the invention and is selected so that the electron donatingability of the phenolic —OH released from the glycosidic bond, thesensitivity to selective cleavage by a desired glycosidase of theglycosidic bond to the carbohydrate moiety Su, and the stability of thequinone methide intermediate upon fragmentation is balanced with theleaving ability of the tertiary amine-containing tubulysin drug so thatefficient release of D from D⁺ through 1,4- or 1,6-elimination occurs.Those Su-O′—Y— structures having a PAB or PAB-type moiety forself-immolation are representative Glucuronide Units. When theglycosidic bond is to the carbohydrate moeity of glucuronic acid, theglycosidase capable of enzymatic cleavage of that glycosidic bond is aglucuronidase.

“Carbohydrate moiety” as used herein refers to a monosaccharide havingthe empirical formula of C_(m)(H₂O)_(n), wherein n is equal to m,containing an aldehyde moiety in its hemiacetal form or a derivativethereof in which a —CH₂OH moiety within that formula has been oxidizedto a carboxylic acid (e.g., glucuronic acid from oxidation of the CH₂OHgroup in glucose). Typically, a carbohydrate moiety (Su) is a cyclichexose, such as a pyranose, or a cyclic pentose, such as a furanose.Usually, the pyranose is a glucuronide or hexose in the β-Dconformation. In some instances, the pyranose is a β-D-glucuronidemoiety (i.e., β-D-glucuronic acid linked to the self-immolative moietyof Y via a glycosidic bond that is cleavable by β-glucuronidase).Oftentimes, the carbohydrate moiety is unsubstituted (e.g., is anaturally occurring cyclic hexose or cyclic pentose). Other times, thecarbohydrate moiety can be a cyclic hexose or cyclic pentose in which ahydroxyl group has been removed or replaced with halogen, or lower alkylor alkylated by lower alkyl.

“Protease” as defined herein refers to a protein capable of enzymaticcleavage of a carbonyl-nitrogen bond such as an amide bond typicallyfound in a peptide. Proteases are classified into major six classes:serine proteases, threonine proteases, cysteine proteases, glutamic acidproteases, aspartic acid proteases and metalloproteases so named for thecatalytic residue in the active site that is primarily responsible forcleaving the carbonyl-nitrogen bond of its substrate. Proteases arecharacterized by various specificities, which are dependent ofidentities of the residues at the N-terminal and/or C-terminal side ofthe carbonyl-nitrogen bond and various distributions.

When W is comprised of amide or other carbonyl-nitrogen containingfunctional group cleavable by a protease that cleavage site isoftentimes limited to those recognized by proteases that are found inhyper-proliferating cells or hyper-stimulated immune cells or withincells particular to the environment in which hyper-proliferating cellsor hyper-stimulated immune cells are present. In those instances, theprotease is not necessarily required to be preferentially present orfound in greater abundance in the cells targeted by the LDC since an LDCwill have poorer access to those cells that do not preferential displaythe targeted moiety. Other times, the protease is preferentiallyexcreted by abnormal cells or by normal cells peculiar to theenvironment in which those abnormal cells are found in comparison to theenvironment normal cells distant from the site of the abnormal cells.Thus, in those instances where the protease is excreted, the protease isnecessarily required to be preferentially present or found in greaterabundance in the vicinity of cells targeted by the LDC in comparison tothat of normal cells not in the vicinity of the abnormal cells.

When incorporated into an LDC, a peptide comprising W will present arecognition sequence to a protease that cleaves a carbonyl-nitrogen bondin W to initiate fragmentation of the Linker Unit so as to cause releaseof an tertiary amine-containing drug from D⁺. Sometimes, the recognitionsequence is selectively recognized by an intracellular protease presentin abnormal cells to which the LDC has preferred access in comparison tonormal cells due to targeting of the abnormal cells, or ispreferentially produced by abnormal cells in comparison to normal cells,for the purpose of appropriately delivering the drug to the desired siteof action. Usually the peptide is resistant to circulating proteases inorder to minimize premature expulsion of the tubulysin drug compound andthus minimize unwanted systemic exposure to that compound. Typically,the peptide will have one or more unnatural or non-classical amino acidsin its sequence in order to have that resistance. Oftentimes, the amidebond that is specifically cleaved by a protease produced by an abnormalcell is an anilide wherein the nitrogen of that anilide is a nascentelectron-donating heteroatom (i.e., J) of an self-immolative moietyhaving the previously defined structures. Thus, protease action on sucha peptide sequence in W results in release of D⁺ as D from the LinkerUnit through a 1,4- or 1,6-elimination proceeding through the centralarylene or heteroarylene moiety of the self-immolative moeity.

Regulatory proteases are typically located intracellularly and arerequired for the regulation of cellular activities that sometimesbecomes aberrant or dysregulated in abnormal or other unwanted cells. Insome instances, when W is directed to a protease having preferentialdistribution intracellularly, that protease is a regulatory proteaseinvolved in cellular maintenance or proliferation. In some instances,those proteases include cathepsins. Cathepsins include the serineproteases, Cathepsin A, Cathepsin G, aspartic acid proteases CathepsinD. Cathepsin E and the cysteine proteases, Cathepsin B, Cathepsin C,Cathepsin F, Cathepsin H, Cathepsin K, Cathepsin L1, Cathepsin L2,Cathepsin O, Cathepsin S, Cathepsin W and Cathepsin Z.

In other instances, when W is directed to a protease that ispreferentially distributed extracellularly in the vicinity ofhyper-proliferating or hyper-stimulated immune cells due to preferentialexcretion by such cells or by neighboring cells whose excretion ispeculiar to the environment of hyper-proliferating or hyper-stimulatedimmune cells, that protease is usually a metalloprotease. Typically,those proteases are involved in tissue remodeling, which aids in theinvasiveness of hyper-proliferating cells or result from undesiredaccumulation of hyper-activated immune cells that results in furtherrecruit of such cells.

“Tubulysin drug” or “tubulysin compound” as used is a peptide-basedtubulin disrupting agent having cytotoxic activity, cytostatic oranti-inflammatory activity and is comprised of one natural or un-naturalamino acid component and three other un-natural amino acid componentswherein one of those components is characterized by a central 5-memberedor 6-membered heteroarylene moiety and another component provides for atertiary amine for incorporation into a quaternized drug unit.

Tubulysin compounds have the structure of D_(G) or D_(H):

wherein the straight dashed line indicates an optional double bond, thecurved dash line indicates optional cyclization, the circled Arindicates an arylene or heteroarylene that is 1,3-substituted within thetubulysin carbon skeleton and is optionally substituted elsewhere,wherein the arylene or heteroarylene and other variable groups are asdefined in the embodiments of the invention.

Naturally-occurring tubulysin compounds have the structure of D_(G-6).

and are conveniently divided into four amino acid subunits, as indicatedby the dashed vertical lines, named N-methyl-pipecolinic acid (Mep),isoleucine (Ile), tubuvaline (Tuv), and either tubuphenylalanine (Tup,when R^(7A) is hydrogen) or tubutyrosine (Tut, when R^(7A) is —OH).There are about a dozen naturally occurring tubulysins presently knownnamed Tubulysin A-I, Tubulysin U. Tubulysin V and Tubulysin Z, whosestructures are indicated by variable groups for structure D_(G-6)defined in in embodiments of tubulysin-based quaternized drug units.

Pretubulysins have the structure D_(G) or D_(H), wherein R³ is —CH₃ andR² is hydrogen, and desmethyl tubulysins have the structure of D_(G),D_(G-1), D_(G-6), D_(H) or D_(H-1) in which R³ is hydrogen and othertubulysin structures given by the embodiments of tubulysin-basedquaternized drug units, wherein R³ is hydrogen, and wherein the othervariable groups as described for tubulysins. Pretubulysins and desmethyltubulysins and are optionally included in the definition of tubulysins.

In structures D_(G), D_(G-1), D_(G-6), D_(H), D_(H-1), and othertubulysin structures described herein in embodiments of tubulysin-basedquaternized Drug Units, the indicated (†) nitrogen atom is the site ofquaternization when such structures correspond to or are incorporatedinto an LDC or precursor thereof as a quaternized tubulysin Drug Unit.When incorporated into an LDC or precursor thereof that nitrogen isquaternized by covalent binding to L_(O) or to L_(O) of an L_(B) orL_(B)′-containing moiety comprised of L_(O). Typically, that quaternizedmoiety of D⁺ results from covalent attachment of the nitrogen atom ofthe tertiary amine moiety to the benzylic carbon of a PAB or PAB-typemoiety in a self-immolative Spacer Unit Y unit of L_(O). Structures ofother exemplary tertiary amine-containing tubulysins and pretubulysinsand manner of their incorporation into an LDC as D⁺ are provided inembodiments of tubulysin-based quaternized drug units.

Exemplary methods of preparing tubulysin drugs and theirstructure-activity relationships are provided by Shankar et al.“Synthesis and structure-activity relationship studies of noveltubulysin U analogs-effect on cytotoxicity of structural variations inthe tubuvaline fragment” Org. Biomol. Chem. (2013) 11: 2273-2287;Xiangming et al. “Recent advances in the synthesis of tubulysins”Mini-Rev. Med. Chem. (2013) 13: 1572-8; Shankar et al. “Synthesis andcytotoxic evaluation of diastereomers and N-terminal analogs ofTubulysin-U” Tet. Lett. (2013) 54: 6137-6141; Shankar et al. “Totalsynthesis and cytotoxicity evaluation of an oxazole analogue ofTubulysin U” Synlett (2011) 2011(12): 1673-6; Raghavan et al. J. Med.Chem. (2008) 51: 1530-3; Balasubramanian, R. et al. “Tubulysin analogsincorporating desmethyl and dimethyl tubuphenylalanine derivatives”Bioorg. Med. Chem. Lett. (2008) 18: 2996-9; and Raghavan et al.“Cytotoxic simplified tubulysin analogues” J. Med. Chem. (2008) 51:1530-3.

“Intracellularly cleaved”, “intracellular cleavage” and like terms usedherein refer to a metabolic process or reaction inside a cell on an LDCor the like, whereby the covalent attachment, e.g., the linker, betweenthe quaternary amine of the quaternized tubulysin compound and theantibody is broken, resulting in the free tertiary amine-containingdrug, or other metabolite of the conjugate dissociated from thetargeting moiety inside the cell. The cleaved moieties of the LDC arethus intracellular metabolites.

“Bioavailability” as used herein refers to the systemic availability(i.e., blood/plasma levels) of a given amount of a drug administered toa patient. Bioavailability is an absolute term that indicatesmeasurement of both the time (rate) and total amount (extent) of drugthat reaches the general circulation from an administered dosage form.

“Subject” as used herein refers to a human, non-human primate or mammalhaving a hyper-proliferation, inflammatory or immune disorder or proneto such disorder that would benefit from administering an effectiveamount of an LDC. Non-limiting examples of a subject include human, rat,mouse, guinea pig, monkey, pig, goat, cow, horse, dog, cat, bird andfowl. Typically, the subject is a human, non-human primate, rat, mouseor dog.

The term “inhibit” or “inhibition of” means to reduce by a measurableamount, or to prevent entirely. Inhibition of proliferation ofhyper-proliferating cells to an ADC is typically determined relative tountreated cells (sham treated with vehicle) in a suitable test system asin cell culture (in vitro) or in a xenograft model (in vivo). Typicallyan LDC comprised of a targeting moiety to an antigen that is not presenton the hyper-proliferating cells or activated immune-stimulating cellsof interest is used as a negative control.

The term “therapeutically effective amount” refers to an amount of adrug effective to treat a disease or disorder in a mammal. In the caseof cancer, the therapeutically effective amount of the drug may reducethe number of cancer cells; reduce the tumor size: inhibit (i.e., slowto some extent and preferably stop) cancer cell infiltration intoperipheral organs: inhibit (i.e., slow to some extent and preferablystop) tumor metastasis; inhibit, to some extent, tumor growth; and/orrelieve to some extent one or more of the symptoms associated with thecancer. To the extent the drug may inhibit growth and/or kill existingcancer cells, it may be cytostatic and/or cytotoxic. For cancer therapy,efficacy can, for example, be measured by assessing the time to diseaseprogression (TTP) and/or determining the response rate (RR).

In the case of immune disorders resulting from hyper-stimulated immunecells, a therapeutically effective amount of the drug may reduce thenumber of hyper-stimulated immune cells, the extent of their stimulationand/or infiltration into otherwise normal tissue and/or relieve to someextent one or more of the symptoms associated with a dysregulated immunesystem due to hyper-stimulated immune cells. For immune disorders due tohyper-stimulated immune cells, efficacy can, for example be measured byassessing one or more inflammatory surrogates, including one or morecytokines levels such as those for IL-1β, TNFα, INFγ and MCP-1, ornumbers of classically activated macrophages.

In some aspects of the invention the Ligand-Drug Conjugate associateswith an antigen on the surface of a targeted cell (i.e., ahyper-proliferating cell or a hyper-stimulated immune cell), and theligand drug conjugate is then taken up inside a target cell throughreceptor-mediated endocytosis. Once inside the cell, one or morecleavage units within the Linker unit are cleaved, resulting in releaseof the tertiary amine-containing drug. The released tertiaryamine-containing tubulysin drug is then free to migrate in the cytosoland induce cytotoxic or cytostatic activities or in the case ofhyper-stimulated immune cells may alternatively inhibit pro-inflammatorysignal transduction. In another aspect of the invention, the quaternizedDrug Unit is cleaved from the Ligand-Drug Conjugate outside the targetcell but within the vicinity of the target cell so that the releasedtertiary amine-containing tubulysin compound subsequently penetrates thecell rather than being released at distal sites.

“Carrier” as the term is used herein refers to a diluent, adjuvant orexcipient, with which a compound is administered. Such pharmaceuticalcarriers can be liquids, such as water and oils, including those ofpetroleum, animal, vegetable or synthetic origin, such as peanut oil,soybean oil, mineral oil, sesame oil. The carriers can be saline, gumacacia, gelatin, starch paste, talc, keratin, colloidal silica, urea. Inaddition, auxiliary, stabilizing, thickening, lubricating and coloringagents can be used. In one embodiment, when administered to a patient,the compound or compositions and pharmaceutically acceptable carriersare sterile. Water is an exemplary carrier when the compounds areadministered intravenously. Saline solutions and aqueous dextrose andglycerol solutions can also be employed as liquid carriers, particularlyfor injectable solutions. Suitable pharmaceutical carriers also includeexcipients such as starch, glucose, lactose, sucrose, gelatin, malt,rice, flour, chalk, silica gel, sodium stearate, glycerol monostearate,talc, sodium chloride, dried skim milk, glycerol, propylene, glycol,water, and ethanol. The present compositions, if desired, can alsocontain minor amounts of wetting or emulsifying agents, or pH bufferingagents.

“Treat”, “treatment,” and like terms, unless otherwise indicated bycontext, refer to therapeutic treatment and prophylactic measures toprevent relapse, wherein the object is to inhibit or slow down (lessen)an undesired physiological change or disorder, such as the developmentor spread of cancer or tissue damage from chronic inflammation.Typically, beneficial or desired clinical results of such therapeutictreatments include, but are not limited to, alleviation of symptoms,diminishment of extent of disease, stabilized (i.e., not worsening)state of disease, delay or slowing of disease progression, ameliorationor palliation of the disease state, and remission (whether partial ortotal), whether detectable or undetectable. “Treatment” can also meanprolonging survival or quality of like as compared to expected survivalor quality of life if not receiving treatment. Those in need oftreatment include those already having the condition or disorder as wellas those prone to have the condition or disorder.

In the context of cancer or a disease state related to chronicinflammation, the term “treating” includes any or all of inhibitinggrowth of tumor cells, cancer cells, or of a tumor; inhibitingreplication of tumor cells or cancer cells, inhibiting dissemination oftumor cells or cancer cell, lessening of overall tumor burden ordecreasing the number of cancerous cells, inhibiting replication orstimulation of pro-inflammatory immune cells, inhibiting or decreasingthe chronic inflammatory state of a dysregulated immune system ordecreasing the frequency and/or intensity of flares experienced bysubjects having an autoimmune condition or disease or ameliorating oneor more symptoms associated with cancer or a hyper-immune stimulateddisease or condition.

“Pharmaceutically acceptable salt” as used herein, refers topharmaceutically acceptable organic or inorganic salts of a compound.The compound typically contains at least one amino group, andaccordingly acid addition salts can be formed with this amino group.Exemplary salts include, but are not limited to, sulfate, citrate,acetate, oxalate, chloride, bromide, iodide, nitrate, bisulfate,phosphate, acid phosphate, isonicotinate, lactate, salicylate, acidcitrate, tartrate, oleate, tannate, pantothenate, bitartrate, ascorbate,succinate, maleate, gentisinate, fumarate, gluconate, glucuronate,saccharate, formate, benzoate, glutamate, methanesulfonate,ethanesulfonate, benzenesulfonate, p-toluenesulfonate, and pamoate(i.e., 1,1′-methylene-bis-(2-hydroxy-3-naphthoate)) salts.

A pharmaceutically acceptable salt may involve the inclusion of anothermolecule such as an acetate ion, a succinate ion or other counterion.The counterion may be any organic or inorganic moiety that stabilizesthe charge on the parent compound. Furthermore, a pharmaceuticallyacceptable salt may have more than one charged atom in its structure.Instances where multiple charged atoms are part of the pharmaceuticallyacceptable salt can have multiple counter ions. Hence, apharmaceutically acceptable salt can have one or more charged atomsand/or one or more counterions. Typically, a quaternized tubulysin DrugUnit is in pharmaceutically acceptable salt form.

Typically, a pharmaceutically acceptable salt is selected from thosedescribed in P. H. Stahl and C. G. Wermuth, editors, Handbook ofPharmaceutical Salts: Properties, Selection and Use,Weinheim/Zürich:Wiley-VCH/VHCA, 2002. Salt selection is dependent onproperties the drug product must exhibit, including adequate aqueoussolubility at various pH values, depending upon the intended route(s) ofadministration, crystallinity with flow characteristics and lowhygroscopicity (i.e., water absorption versus relative humidity)suitable for handling and required shelf life by determining chemicaland solid-state stability under accelerated conditions (i.e., fordetermining degradation or solid-state changes when stored at 40° C. and75% relative humidity).

“Loading”. “drug loading”, “payload loading” or like terms represent orrefer to the average number of payloads (“payload” and “payloads” areused interchangeable herein with “drug” and “drugs”) in an population ofLDCs (i.e., a composition of LDC differing in number of attached D⁺units having either the same or different attachment locations, butotherwise essentially identical in structure). Drug loading may rangefrom 1 to 24 drugs per targeting moiety. That is sometimes referred toas the DAR, or drug to targeting moiety ratio. Compositions of LDCsdescribed herein typically have DAR's of from 1-24 or 1-20, and in someaspects from 1-8, from 2-8, from 2-6, from 2-5 and from 2-4. Typical DARvalues are about 2, about 4, about 6 and about 8. The average number ofdrugs per antibody, or DAR value, may be characterized by conventionalmeans such as UV/visible spectroscopy, mass spectrometry, ELISA assay,and HPLC. A quantitative DAR value may also be determined. In someinstances, separation, purification, and characterization of homogeneousLDCs having a particular DAR value may be achieved by means such asreverse phase HPLC or electrophoresis. DAR may be limited by the numberof attachment sites on the targeting moiety.

For example, when the targeting moiety is an antibody and the attachmentsite is a cysteine thiol, an antibody may have only one or severalsufficiently reactive thiol groups that react with a L_(B)′-containingmoiety. Sometimes, the cysteine thiol is a thiol group derived from of acysteine residue that participated in an interchain disulfide bond.Other times, the cysteine thiol is a thiol group of a cysteine residuethat did not participate in an interchain disulfide bond, but wasintroduced through genetic engineering. Typically, less than thetheoretical maximum of D⁺ moieties is conjugated to an antibody during aconjugation reaction. For example, an antibody may contain many lysineresidues that do not react with a L_(B)′-containing moiety, since onlythe most reactive lysine groups may react with that moiety.

I. Embodiments

Provided herein are Ligand-drug conjugates (LDCs) capable ofpreferential delivery of a tertiary amine-containing tubulysin compoundto hyperproliferating cells or hyper-activated immune cells or to thevicinity of such abnormal cells in comparison to normal cells or theenvironment of normal cells where the abnormal cells are typically notpresent and are thus useful for treating diseases and conditionscharacterized by these abnormal cells.

1.1 General

A LDC has three major components: (1) a Ligand Unit corresponding to orincorporating a targeting agent that selectively binds to a targetedmoiety present on, within or in the vicinity of abnormal cells or otherunwanted cells in comparison to other moieties present on, within, or inthe vicinity of normal cells where these abnormal or unwanted cells aretypically not present, or is present on, within, or in the vicinity ofabnormal or other unwanted cells in greater abundance in comparison tonormal cells or the environment of normal cells where abnormal orunwanted cells are typically not present, (2) a quaternized tubulysinDrug Unit (D⁺) incorporating or corresponding to the structure of atertiary amine-containing tubulysin compound by quaternization of thetertiary amine nitrogen atom and (3) a Linker Unit that connects D⁺ tothe Ligand Unit and is capable of conditionally releasing free tertiaryamine-containing tubulysin drug within or in the vicinity of abnormal orunwanted cells that are targeted by the Ligand Unit.

A tubulysin compound to be used in the present invention is one thatprimarily or selectively exerts its effect (e.g., cytotoxic, cytostaticeffect) on mammalian cells as compared to prokaryotic cells. In someaspects the targeted moiety is an epitope of an extracellular displayedmembrane protein that is preferentially found on abnormal or unwantedcells in comparison to normal cells. Specificity towards the abnormal orunwanted cells (i.e., the targeted cells) results from the Ligand Unit(L) of the LDC into which D is incorporated. In addition to L and D⁺, anLDC that targets abnormal or unwanted cells has a Linker Unit thatcovalently interconnects a quaternized tubulysin Drug Unit with theLigand Unit. In some aspects the Ligand Unit is from an antibody, whichis an exemplary targeting agent, which recognizes abnormal mammaliancells.

In some aspects the targeted moiety recognized by the Ligand Unit is anepitope of an extracellular displayed membrane protein that ispreferentially found on abnormal or unwanted cells in comparison tonormal cells. In some of those aspects, and as a further requirement,the membrane protein targeted by the Ligand Unit must have sufficientcopy number and be internalized upon binding of the LDC in order tointracellularly deliver an effective amount of the cytotoxic,cytostatic, immune-suppressive or anti-inflammatory tubulysin compoundpreferentially to the abnormal cells.

A tertiary-amine containing tubulysin compound typically exhibitsadverse peripheral effects when administered in unconjugated form.Therefore, that compound needs to be selectively delivered by its LDC sothat the Linker Unit of an LDC is not merely a passive structure thatserves as a bridge between a targeting Ligand Unit and D⁺ from which thetubulysin compound is released, but must be carefully engineered to havestability from the site of administration of the LDC until its deliveryto the targeted site and then must efficiently release an activetubulysin compound. To accomplish that task, a targeting agent isreacted with a L_(B)′-containing moiety to form a L_(B)-containingmoiety within a Ligand Drug Conjugate. When the L_(B)-containing moietyis so formed, the resulting Ligand Drug Conjugate is typically comprisedof the targeting moiety (in the form of a Ligand Unit), a LigandCovalent Binding Unit (L_(B)), also referred to as a primary linker(L_(R)), a quaternized tubulysin compound (D⁺) and a secondary linker(L_(O)) intervening between L_(B) and D⁺.

1.1 Primary Linker (L_(R))

A primary linker (L_(R)) is a Ligand Covalent Binding Unit (L_(B)) or aLigand Covalent Binding Unit precursor (L_(B)′) and typically is presentas a component of a Linker Unit of a LDC or of a L_(B)′-containingmoiety such as L_(B)′-L_(O) in a Drug Linker compound having the formulaL_(B)′-L_(O)-D⁺. The primary linker of a L_(B)′-containing moiety iscomprised of a functional group capable of reacting with anelectrophilic or nucleophillic functional group of a targeting agent. Asa result of that reaction, the targeting agent becomes covalently bondedas a Ligand Unit to a primary linker through L_(B), wherein the primarylinker is now L_(B) having a functional group derived from L_(B)′.

In some embodiments L_(B)′ in a L_(B)′-containing moiety has thestructure of one of

wherein R is hydrogen or C₁-C₆ optionally substituted alkyl; T is —Cl,—Br, —I, —O-mesyl, —O-tosyl or other sulfonate leaving group; U is —F,—Cl, —Br, —I, —O—N-succinimide, —O-(4-nitrophenyl),—O-pentafluorophenyl, tetrafluorophenyl or —O—C(═O)—OR⁵⁷; X² is C₁₋₁₀alkylene, C₃-C₈-carbocycle, —O—(C₁-C₆ alkyl), -arylene-, C₁-C₁₀alkylene-arylene, -arylene-C₁-C₁₀ alkylene, —C₁-C₁₀alkylene-(C₃-C₆-carbocycle)-, —(C₃-C₈ carbocycle)-C₁-C₁₀ alkylene-,C₃-C₈-heterocycle, —C₁-C₁₀ alkylene-(C₃-C₈ heterocyclo)-,—C₃-C₈-heterocyclo)-C₁-C₁₀ alkylene, —(CH₂CH₂O)_(u), or—CH₂CH₂O)_(u)—CH₂—, wherein u is an integer ranging from 1 to 10 and R⁵⁷is C₁-C₆ alkyl or aryl; and wherein the wavy line indicates covalentbinding to a subunit of L_(O).

On interaction with an electrophile or nucleophile of a targeting agentL_(B)′ is converted to Ligand-L_(B)- moiety as exemplified below whereone such interaction has taken place:

wherein the indicated (#) atom is derived from the reactive moiety ofthe ligand and X² is as defined.

1.2 Secondary Linkers (L_(O))

Secondary linkers in a LDC or a L_(B)′-containing precursor thereof, isan organic moiety situated between the primary linker (L_(B)) and thequaternized drug unit (D⁺) that provides for processing of a CleavableUnit (W or W′) within the LDC's Linker Unit subsequent to selectivebinding of the LDC's targeting moiety to its cognate target moietypresent on, within or in the vicinity of hyper-proliferating cells,hyper-activated immune cells or other abnormal or unwanted cellstargeted by the LDC. In some embodiments W provides a substrate for aprotease that is present within hyper-proliferating cells orhyper-activated immune cells. Preferred are those cleavage units thatare not recognized by proteases excreted by normal cells that are nottypically in the presence of hyper-proliferating cells orhyper-activated immune cells or are substrates for proteases havingsystemic circulation in order to minimize non-targeted drug release orsystemic exposure to the tertiary amine-containing drug due itspremature released from its LDC. More preferred are those proteases thatare regulatory proteases or proteases found in lysosomes, which arecellular compartments to which an LDC is delivered upon internalizationof a membrane-surface receptor to which the LDC has specifically bound.Regulatory and lysosomal proteases are exemplary intracellularproteases.

In one embodiment W within a secondary linker is comprised or consistsof a dipeptide moiety having the structure of:

wherein R²⁹ is benzyl, methyl, isopropyl, isobutyl, sec-butyl,—CH(OH)CH₃ or has the structure of

and R³⁰ is methyl, —(CH₂)₄—NH₂, —(CH₂)₃NH(C═O)NH₂, —(CH₂)₃NH(C═NH)NH₂,or, —(CH₂)₂CO₂H, wherein the dipeptide moiety provides for a recognitionsite for a regulatory or lysosomal protease.

In preferred embodiments the dipeptide is valine-alanine (val-ala). Inanother preferred embodiment. W is comprised or consists of thedipeptide valine-citrulline (val-cit). In another preferred embodiment Wis comprised or consists of the dipeptide threonine-glutamic acid(thr-glu). In other embodiments W is a single naturally-occurringL-amino acid, preferably L-glutamate or L-lysine. In some of thoseembodiments the dipeptide moiety or L-amino acid is covalently attachedto a self-immolative moeity (SI) of Y through an amide bond formedbetween the alanine or citrulline carboxylic acid functional group orthe alpha carboxylic acid functional group of glutamate and an aryl orheteroaryl amino group of SI. Thus, in those embodiments SI is comprisedof an arylamine or heteroarylamine moiety and the aforementionedcarboxylic acid functional group of a dipeptide moiety forms an anilidebond with the amino nitrogen that arylamine moiety.

In another embodiment, W′ within a secondary linker is comprised of aglycoside-bonded carbohydrate moiety having a recognition site for anintracellularly located glycosidase. In those embodiments W′ is acarbohydrate moiety bonded to E′ through a glycosidic bond wherein W′-E′provides the recognition site for cleavage of W′ from E′, and wherein E′is an optionally substituted heteroatom, of which a self-immolativeSpace Unit to which W′ is attached within a Glucuronide Unit of formula—Y(W′)— is comprised. In those embodiments W′-E′- typically has thestructure of

wherein R⁴⁵ is —CH₂OH or —CO₂H and E′ is a heteroatom moiety such as—O—, —S— or —NH— bonded to the carbohydrate moiety and to aself-immolative moiety of Y (as indicated by the wavy line) wherein thebond to the carbohydrate moiety provides for a recognition site for aglycosidase. Preferably that site is recognized by a lysosomeglycosidase. In some embodiments the glycosidase is a glucuronidase aswhen R⁴⁵ is —CO₂H.

A Secondary Linker Unit (L_(O)) in addition to W or W′ are alsocomprised of a spacer (Y) unit and a -L_(P)(PEG)- moiety and may beadditionally comprised of second stretcher (A_(O)) or a Branching Unit(B) arranged with respect to W/W′ in a linear relationship representedby L_(O)-D⁺ structures of (1a) and (1b), or an orthogonal relationshiprepresented by L_(O)-D⁺ structures of (2a) and (2b), respectively

wherein A_(a) is a first optional Stretcher unit, A_(O) is a secondoptional Stretcher Unit; W_(w) and W′_(w′) are Cleavable units; andY_(y) is a Spacer unit, wherein subscripts a and b are independently 0or 1, subscript w or w′ is 1 and subscript y is 1. When subscript a is 1the wavy line before A_(a) indicates covalent bonding of that L_(O)subunit to L_(B)′ or L_(B)(resulting from L_(B)′ after its incorporationinto an LDC). When subscript a is 0 that wavy line indicates covalentbinding of L_(B)′ or L_(B) to the -L_(P)(PEG)- moiety in structure (1a),(1b) (2a) or (2b).

In preferred embodiments subscript a is 1. In other preferredembodiments -L_(O)-D⁺ has the structure of (2a) or 2(b), more preferablywhen A_(O) is present or subscript b is 0. In particularly preferredembodiments -L_(O)-D⁺ has the structure of (2a), wherein A_(O) ispresent and subscript a is 1 so that A is also present.

Structures of some exemplary A/A_(O), W and Y moieties in L_(O) andtheir substituents are described in WO 2004/010957, WO 2007/038658, U.S.Pat. Nos. 6,214,345, 7,498,298, 7,968,687 and 8,163,888, and US Pat.Publ. Nos. 2009-0111756, 2009-0018086 and 2009-0274713 which areincorporated by reference herein.

In some embodiments A_(O), A, or subunits thereof have the structure of

wherein the wavy lines indicated covalent attachment within theremainder of L_(O), and wherein for A_(O) the wavy line to the carbonylmoiety in either structure within (1a) represents the point ofattachment to the amino terminus of a dipeptide moiety or anaturally-occurring L-amino acid comprising W when Y is arrangedlinearly with respect to Y and D⁺ or within (2b) represents the point ofattachment to a self-immolating moiety of Y described herein to which W′is bonded to Y and is arranged orthogonal with respect to Y and D⁺, andwherein the wavy line to the amino moiety of either structure representswithin (1a) or (2a) the point of attachment to a carbonyl-containingfunctional group of L_(P) in -L_(P)(PEG);

wherein K and L independently are C, N, O or S, provided that when K orL is O or S, R⁴¹ and R⁴² to K or R⁴³ and R⁴⁴ to L are absent, and when Kor L are N, one of R⁴¹, R⁴² to K or one of R⁴², R⁴³ to L are absent, andprovided that no two adjacent L are independently selected as N, O, orS;

wherein subscripts e and f are independently selected integers thatrange from 0 to 12, and subscript g is an integer ranging from 1 to 12:

wherein G is hydrogen, optionally substituted C₁-C₆ alkyl, —OH,—OR^(PR), —CO₂H, CO₂R^(PR), wherein R^(PR) is a suitable protecting,—N(R^(PR))(R^(PR)), wherein R^(PR) (are independently a protecting groupor R^(PR) together form a suitable protecting group, or —N(R⁴⁵)(R⁴⁶),wherein one of R⁴⁵, R⁴⁶ is hydrogen or R^(PR), wherein R^(PR) is asuitable protecting group, and the other is hydrogen or optionallysubstituted C₁-C₆ alkyl;

wherein R³⁸ is hydrogen or optionally substituted C₁-C₆ alkyl; R³⁹—R⁴⁴independently are hydrogen, optionally substituted C₁-C₆ alkyl,optionally substituted aryl, or optionally substituted heteroaryl, orboth R³⁹, R⁴⁰ together with the carbon to which they are attachedcomprise a C₃-C₆ cycloalkyl, or R⁴¹, R⁴² together with K to which theyare attached when K is C, or R⁴³, R⁴⁴ together with L to which they areattached when L is C comprise a C₃-C₆ cycloalkyl, or R⁴⁰ and R⁴¹, or R⁴⁰and R⁴³, or R⁴¹ and R⁴³ to together with the carbon or heteroatom towhich they are attached and the atoms intervening between those carbonand/or heteroatoms comprise a 5- or 6-membered cycloalkyl orheterocycloalkyl, provided that when K is O or S. R⁴¹ and R⁴² areabsent, when K is N, one of R⁴¹, R⁴² is absent, when L is O or S, R⁴³and R⁴⁴ are absent, and when L is N, one of R⁴³, R⁴ is absent.

In some embodiments R³⁸ is hydrogen. In other embodiments —K(R⁴¹)(R⁴²)is —(CH₂)—. In other embodiments when subscript e is not 0, R³⁹ and R⁴⁰are hydrogen in each occurrence. In other embodiments when subscript fis not 0, -L(R⁴³)(R⁴⁴)— is —CH₂— in each occurrence.

In preferred embodiments G is —CO₂H. In other preferred embodiments Kand/or L are C. In other preferred embodiments subscript e or f is 0. Instill other preferred embodiments e+f is an integer ranging from 1 to 4.

In some embodiments A_(O), A, or a subunit thereof has the structure of—NH—C₁-C₁₀ alkylene-C(═O)—, —NH—C₁-C₁₀ alkylene-NH—C(═O)—C₁-C₁₀alkylene-C(═O)—, —NH—C₁-C₁₀ alkylene-C(═O)—NH—C₁-C₁₀ alkylene (C═O)—,—NH—(CH₂CH₂O)_(s)—CH₂(C═O)—, —NH—(C₃-C₈ carbocyclo)(C═O)—,—NH-(arylene-)—C(═O)—, and —NH—(C₃-C₈ heterocyclo-)C(═O).

In other embodiments A_(O), A, or a subunit thereof has the structure of

wherein R¹³ is —C₁-C₁₀ alkylene-, —C₃-C₈carbocyclo-, -arylene-,—C₁-C₃₀heteroalkylene-, —C₃-C₈heterocyclo-, —C₁-C₁₀alkylene-arylene-,-arylene-C₁-C₁₀alkylene-, —C₁-C₁₀ alkylene-(C₃-C₈carbocyclo)-,—(C₃-C₈carbocyclo)-C₁-C₁₀alkylene-, —C₁-C₁₀ alkylene-(C₃-C₈heterocyclo)-, —(C₃-C₈ heterocyclo)-C₁-C₁₀ alkylene-,—(CH₂CH₂O)₁₋₁₀(—CH₂)₁₋₃—, or —(CH₂CH₂NH)₁₋₁₀(—CH₂)₁₋₃—. In someembodiments, R¹³ is —C₁-C₁₀ alkylene- or —C₁-C₃₀heteroalkylene-. In someembodiments, R¹³ is —C₁-C₁₀ alkylene-, —(CH₂CH₂O)₁₋₁₀(—CH₂)₁₋₃—, or—(CH₂CH₂NH)₁₋₁₀(—CH₂)₁₋₃. In some embodiments, R¹³ is —C₁-C₁₀alkylene-polyethylene glycol, or polyethyleneimine.

In more preferred embodiments A_(O), A, or a subunit thereof correspondsin structure to or is a residue of an alpha-amino acid-, a beta-aminoacid moiety, or other amine-containing acid. Other embodiments of A as asingle unit and subunits A₁₋₄ of A are described in embodiments forLinker Units having the formula of L_(R)-L_(O).

In some embodiments, Spacer Units are capable of undergoing a 1,4- or1,6-elimination reaction subsequent to enzymatic processing of Wcovalently bonded to Y (i.e., Y is comprised of a self-immolative SpacerUnit). In some embodiments Y-D⁺ arranged linearly with W in L_(O) hasthe structure of:

wherein V, Z¹, Z² and Z³ independently are —C(R²⁴)═ or —N═; U is —O—,—S— or —N(R³⁵)—; R²⁴ independently are hydrogen, halogen, —NO₂, —CN,—OR²⁵, —SR²⁶, —N(R²⁷)(R²⁸), optionally substituted C₁-C₆ alkyl, or—C(R²⁹)═C(R³⁰)—R³¹, wherein R²⁵ is hydrogen, optionally substitutedC₁-C₆ alkyl, optionally substituted aryl or optionally substitutedheteroaryl, R²⁶ is optionally substituted C₁-C₆ alkyl, optionallysubstituted aryl or optionally substituted heteroaryl, R²⁷ and R²⁸independently are hydrogen, optionally substituted C₁-C₆ alkyl,optionally substituted aryl or optionally substituted heteroaryl or bothR²⁷ and R²⁸ together with the nitrogen to which they are attachedcomprises a 5- or 6-membered heterocycle. R²⁹ and R³⁰ independently arehydrogen, or optionally substituted C₁-C₆ alkyl, and R¹ is hydrogen,optionally substituted C₁-C₆ alkyl, optionally substituted aryl,optionally substituted heteroaryl, —C(═O)OR³² or —C(═O)NR³², wherein R³²is hydrogen, optionally substituted C₁-C₆ alkyl, optionally substitutedaryl, or optionally substituted heteroaryl, R⁸ and R⁹ independently arehydrogen or optionally substituted C₁-C₆ alkyl; and R′ is hydrogen or ishalogen, —NO₂, —CN or other electron withdrawing group or is an electrondonating group, provided that no more than two of R²⁴ are other thanhydrogen; wherein J is —O—, S—, or —N(R³³)—, wherein R³³ is hydrogen ormethyl;

wherein the wavy line to J represents covalent bonding of J comprising afunctional group of W that inhibits the electron donating ability of Jsufficiently to stabilizes the (hetero)arylene moiety of SI to 1,4- or1,6-elimination and wherein enzymatic processing of W results indis-inhibition of that ability to trigger the elimination so as torelease D⁺ bonded to Y as a tertiary amine-containing tubulysin drug(e.g., when J is bonded to the carbonyl moiety of a carbonyl-containingfunctional group of W);

In other embodiments W′ and Y are arranged orthogonally in L_(O)(i.e.,is —Y(W′)-within the Linker Unit) wherein SI of Y is bonded to aglycoside-bonded carbohydrate moiety having a recognition site for aglycosidase wherein the orthogonal arrangement involving SI of Y istypically represented by the structure of

wherein E′ is bonded to one of V, Z¹, Z³, provided that the other V, Z¹,Z² (i.e., not bonded to E′) is defined by ═C(R²⁴)— or ═N—. In preferredembodiments the orthogonal arrangement involving SI of Y is representedby the structure of

wherein V, Z¹ and Z² independently are —C(R²⁴)═ or —N═; R²⁴independently are hydrogen, halogen, —NO₂, —CN, —OR²⁵, —SR²⁶,—N(R²⁷)(R²⁸), —C(R²⁹)═C(R³⁰)—R³¹ or optionally substituted C₁-C₆;

wherein R²⁵ is hydrogen, optionally substituted C₁-C₆ alkyl, optionallysubstituted aryl or optionally substituted heteroaryl; R²⁶ is optionallysubstituted C₁-C₆ alkyl, optionally substituted aryl or optionallysubstituted heteroaryl, and R²⁷ and R²⁸ independently are hydrogen,optionally substituted C₁-C₆ alkyl, optionally substituted aryl oroptionally substituted heteroaryl or both R²⁷ and R²⁸ together with thenitrogen to which they are attached comprise or define a 5- or6-membered heterocycle, R²⁹ and R³⁰ independently are hydrogen, oroptionally substituted C₁-C₆ alkyl, and R³¹ is hydrogen, optionallysubstituted C₁-C₆ alkyl, optionally substituted aryl, optionallysubstituted heteroaryl, —CN, —C(═O)OR³² or —C(═O)NR³²; wherein R³² ishydrogen, optionally substituted C₁-C₆ alkyl, optionally substitutedaryl, or optionally substituted heteroaryl;

R⁸ and R⁹ independently are hydrogen or optionally substituted C₁-C₆alkyl; R′ is hydrogen or is halogen, —NO₂, —CN or other electronwithdrawing group, or is an electron withdrawing group; R⁴⁵ is —CH₂OH,—CO₂H; E′ is —O— or —NH—; J′ is —NH—; and D⁺ is as defined inembodiments described for quaternized drug units.

In more preferred embodiments the orthogonal arrangement involving SI ofY has the structure of:

In preferred embodiments -E′- is —O— or —NH— and V or Z³ is ═C(R²⁴),wherein R²⁴ is hydrogen or an electron withdrawing group. In otherpreferred embodiments R⁸ and R⁹ are hydrogen and V, Z¹ or Z² is ═CH—. Inother preferred embodiments -J′- is —NH, V, Z¹ or Z² is ═CH— and R′ ishydrogen or an electron withdrawing group, preferably —Cl, —F or —NO₂.

1.3 L_(R)-L_(O) as Linker Units

The quaternary drug unit (D⁺) attached to any of the aboveself-immolative moieties disclosed herein represents any quaternizedtubulysin compound in which the tertiary amine of the C-terminalcomponent of a tubulysin compound is quaternized (i.e., D⁺ is aquaternized tertiary amine-containing tubulysin compound) in which thequaternized nitrogen is attached to the benzylic position of an SImoiety in a self-immolative Spacer Unit.

In some embodiments, -L_(B)-L_(O)-D⁺ or L_(B)′-L_(O)-D⁺ has thestructure of:

wherein V, Z¹ and Z² are independently ═N— or ═C(R²⁴)—, wherein R²⁴,independently selected, is hydrogen, optionally substituted alkyl or anelectron donating group, and R⁸ and R⁹ independently are hydrogen oroptionally substituted alkyl and J is —O— or —N(R³³), wherein R³³ ishydrogen or lower alkyl.

In preferred embodiments where A, W and Y are in a linear configuration,-L_(B)-L_(O)-D⁺ or L_(B)′-L_(O)-D⁺ has the structure of:

In more preferred embodiments where A, W and Y are in a linearconfiguration, a Ligand Drug Conjugate or a Drug Linker compound offormula L_(R)-L_(O)-D⁺ has the structure of:

wherein W is a naturally occurring L-amino acid residue or aresequential Amino Acid subunits so that W consists or is comprised of adipeptide wherein the dipeptide is at the distal end of W wherein thedipeptide and the indicated bond is an amide bond specifically cleavableby an intracellular protease in comparison to freely circulating serumproteases. In preferred embodiments the Amino Acid subunit attached toJ/NH of Y is a natural L-amino acid or an un-natural amino acid whoseamine-bearing carbon is of the same stereochemical configuration.

In any one of the above embodiments where W is comprised of a dipeptidethat is recognized by a intracellular protease, preferably a cathepsinprotease, preferred dipeptides have the structure of

wherein R³⁴ is benzyl, methyl, isopropyl, isobutyl, sec-butyl,—CH(OH)CH₃ or has the structure of

and R³⁵ is methyl, —(CH₂)₄—NH₂, —(CH₂)₃NH(C═O)NH₂, (CH₂)₃NH(C═NH)NH₂, or—(CH₂)₂CO₂H, wherein the wavy line at the dipeptide N-terminal indicatescovalent binding to A or to L_(B) or L_(B)′ and the wavy line at thedipeptide C-terminal indicates covalent binding to J.

In preferred embodiments -L_(B) and L_(B)′ are succinimide (M²) ormaleimide (M¹) moieties, respectively. In those embodiments -L_(B)-A-and -L_(B)-A₁-A₂- are referred to as succinimide-containing moieties,which are representative L_(SS) moieties when A or A₁ is comprised of aBasic Unit, and L_(B)′-A, and L_(B)′-A₁- are referred to asmaleimide-containing moieties, which are precursors to representativeL_(SS) moieties when A or A₁ is comprised of a Basic Unit.

Preferably. A_(O), when A_(O) is present, in any one of the aboveL_(R)-L_(O) structures in which W, Y and D⁺ are in a linearconfiguration corresponds in structure to an amine-containing acid or isan amine-containing acid residue wherein the carboxylic acid terminus ofthe amine-containing acid is bonded to W as an ester or amide,preferably as amide, and its N-terminus is bonded to L_(P) of-L^(P)(PEG)- through a carbonyl-containing functional group.

In other preferred embodiments, -L_(B)-L_(O)-D⁺ or L_(B)′-L_(O)-D⁺ hasthe structure of:

wherein V and Z³ independently are ═N— or ═C(R²⁴)—, wherein R²⁴,independently selected, is hydrogen, optionally substituted alkyl or anelectron donating group, R⁸ and R⁹ independently are hydrogen oroptionally substituted alkyl, and J′ is —O— or —N(R³³), wherein R³³ ishydrogen or lower alkyl, and R′ is hydrogen or an electron withdrawinggroup.

In other more preferred embodiments L_(R)-L_(O)-D⁺ (i.e.,-L_(B)-L_(O)-D⁺ or L_(B)′-L_(O)-D⁺) has the structure of

wherein V, Z¹ or Z³ is ═N— or ═C(R²⁴)—, wherein R²⁴, independentlyselected, is hydrogen, optionally substituted alkyl or an electrondonating group, R⁸ and R⁹ independently are hydrogen or optionallysubstituted alkyl, and J′ is —O— or —N(R³³), wherein R³³ is hydrogen orlower alkyl, R′ is hydrogen or an electron withdrawing group and O′represents a glycosidic-bonded oxygen, the bond to which is cleavable bya glycosidase. In preferred embodiments J′ is —NH—.

Preferably. A_(O), when A_(O) is present, in any one of the aboveL_(B)-L_(O)- structures corresponds in structure to an amine-containingacid wherein the carboxylic acid terminus of the amine-containing acidis bonded to J/J′ as an ester or amide, preferably as amide and itsN-terminus is bonded to Le through a carbonyl-containing functionalgroup.

In particularly preferred embodiments, -L_(B)-A- or L_(B)′-A in any oneof the above -L_(B)-L_(O)-D⁺, L_(B)′-L_(O)-D⁺ or L_(B)-L_(o)-D⁺embodiments has the structure of M¹-A, M¹-A₁-A₂-, M²A or M²-A₁-A₂-represented by:

wherein A₁ and A₂ are subunits of A, L_(B) is a succinimide (M²) moietyand L_(B)′ is a maleimide moiety (M¹), wherein—[C(R^(b1))(R^(b1))]_(q)—[HE]- is A or a subunit (A₁) of A; R and R^(a2)independently are hydrogen or optionally substituted alkyl; R^(a1) ishydrogen, lower alkyl or BU; HE is an optional hydrolysis enhancer (HE)unit; subscript q is an integer ranging from 0 to 6; each R^(b1)independently is hydrogen, optionally substituted C₁-C₆ alkyl,optionally substituted aryl or optionally substituted heteroaryl, or twoR^(b1) together with the carbon(s) to which they are attached compriseor define a C₃-C₆ cycloalkyl or one R^(b1) and HE together with thecarbon to which they are attached comprise or define a 5 or 6-memberedcycloalkyl or a 5- or 6-membered heterocycloalkyl and the other R^(b1)is hydrogen, optionally substituted C₁-C₆ alkyl, optionally substitutedaryl or optionally substituted heteroaryl; BU is a basic unit having thestructure of —[C(R¹)(R¹)]—[C(R²)(R²)]_(n)—N(R²²)(R²³), wherein subscriptn is 0, 1, 2 or 3, R¹ independently are hydrogen or lower alkyl or twoR¹ together with the carbon to which they are attached comprise ordefine a C₃-C₆ cycloalkyl, R² independently are hydrogen, optionallysubstituted C₁-C₆ alkyl, optionally substituted aryl or optionallysubstituted heteroaryl, or two R² together with the carbon(s) to whichthey are attached and any intervening carbons define a C₃-C₆ cycloalkyl,or one R¹ and one R² together with the carbons to which they areattached and any intervening carbons comprise or define a 5- or6-membered cycloalkyl and the remaining R¹ and R² are as defined; R²²and R²³ independently are hydrogen or optionally substituted C₁-C₆ alkylor R²² and R²³ together with the nitrogen to which they are attachedcomprise or define a 5- or 6-membered heterocycloalkyl or one of R²²,R²³ is hydrogen and the other is an acid-labile protecting group; andwherein a sulfhydryl moiety of a targeting agent is bonded to M² as atargeting Ligand Unit as indicated by the wavy line to the succinimidemoiety and wherein the wavy line to HE (or to [C(R^(b1))(R^(b1))]_(q)when HE is not present) indicates covalent binding to another subunit ofA or to -L_(P)(PEG)-.

In other particularly preferred embodiments, -L_(B)-A- or -L_(B)-A₁-A₂-in any one of the above L_(B)-containing embodiments has the structureof -M³-A- or -M³-A₁-A₂-represented by:

wherein A₁ and A₂ are subunits of A, and M^(3A) and M^(3B) areregioisomers of M³ and wherein the variable groups and connectivity to asulfhydryl group of a targeting moiety and HE (or[C(R^(b1))(R^(b1))]_(q)) are as defined for the correspondingsuccinimide-containing moieties shown immediately above. In the presentembodiments L_(B) is referred to as a succinic acid-amide (M³) moietyand -L_(B)-A-, L_(B)′-A-, -L_(B)-A₁- or L_(B)′-A₁- are referred to assuccinic acid-amide-containing moieties, which are representative Lsmoieties.

In those and any one of the above embodiments comprised of HE, HE ispreferably —C(═O)—.

In any one of those -L_(B)-A-, L_(B)′-A-, -L_(B)-A₁- and L_(B)′-A₁- orM¹-A, M¹-A₁-A₂-, M²-A-, M²-A₁-A₂-, M³-A- and M³-A₁-A₂- embodiments eachR^(b) independently is preferably hydrogen or lower alkyl and subscriptm is 0 or 1, R^(a1) is preferably hydrogen, lower alkyl or BU or R² ispreferably hydrogen.

In any one of the above embodiments where W, Y and D⁺ are in a linearconfiguration and is comprised of A or A₁-A₂, preferred embodiments arethose where W is bonded to A or A₂ through an amide functional group. Inthose embodiments preferably A, A, and A₂ have independently selectedstructures corresponding to or incorporating amine-containing acids asdescribed herein for Stretcher Unit embodiments. In any one of the above-L_(B)-A-, L_(B)′-A-, -L_(B)-A₁- and L_(B)′-A₁- embodiments comprised ofA or A₁, A and A₁ preferably have structures corresponding toincorporating amine-containing acids or are amine-containing acidresidues as described herein for Stretcher Unit embodiments wherein A isbonded to W or A, is bonded to A, through an amide functional group. Inany one of the above M¹-A-, M¹-A₁-A₂-, M²-A-, M²-A₁-A₂-, M³-A- andM¹-A₁-A₂-embodiments, preferably A, A₁ and A₂ have independentlyselected structures corresponding to or incorporating amine-containingacids or are independently selected amino acid residues as describedherein for first Stretcher Unit A and second Stretcher Unit A_(O)embodiments. In any one of the above L_(SS) or L_(S) embodiments thatare comprised of -A(BU)- or -A₁(BU)- moieties, A and A₁ preferably havestructures corresponding to or incorporating amine-containing acidssubstituted with BU, and are therefore diamino-containing acids asdescribed herein for Stretcher Unit and Basic Unit embodiments. In M¹,M² and M³-containing moieties having A or A₁ moieties corresponding instructure to or residue of an amine-containing acid, the amine nitrogenof the amine-containing acid is incorporated as the imine nitrogen ofthe M¹ or M² ring system or the amide nitrogen of the M³ moiety. InL_(SS) or L_(S)-containing moieties the N-terminal amine nitrogen of thediamino-containing acid is incorporated as the imine nitrogen of the M¹or M² ring system or the amide nitrogen of the M³ moiety. Preferably forany one of the above M¹-, M²- and M³-containing moieties or L_(SS)- orL_(S)-containing moieties the carboxylic acid of the amine-containingacid or the diamino-containing acid is incorporated into an amidefunctional group to A₂ for those moieties comprised of A₁-A₂- or to Wfor those moieties comprised of A when A is a single unit.

In more preferred embodiments A or A₁ and A₂ in -A₁-A₂- areindependently represented by structures (3) or (4):

wherein L is absent (i.e., subscript e is 0) and G is hydrogen, BU,—CO₂H or —NH₂ or the side chain of a naturally occurring amino acid suchas aspartic acid, glutamic acid or lysine and the other variable groupare as previously defined. In other preferred embodiments L and K arecarbon and R⁴¹, R⁴², R⁴³ and R⁴⁴ in each occurrence is hydrogen andR³⁸—R⁴⁰ and subscripts e, f and g are as previously defined. In otherpreferred embodiments R³⁸—R⁴⁰ in each occurrence is hydrogen and K, Land subscripts e, f and g are as previously defined. Other preferredembodiments have structure (3) wherein K is nitrogen and one of R⁴¹, R⁴²is absent and the other is hydrogen and L, subscripts e, f and g and theremaining R³⁹—R⁴² variable groups are as previously defined. Otherpreferred embodiments have structure (4) wherein subscript g is 1. K isnitrogen and one of R⁴¹, R⁴² is absent and the other is hydrogen, L,subscripts e and f and the remaining R³⁹—R⁴² variable groups are aspreviously defined. In other preferred embodiments subscripts e and f ofstructure (3) are each 0 or subscripts f and g of structure (4) are each0, wherein K, L and the remaining R³⁸—R⁴⁴ variable groups are aspreviously defined. Other preferred embodiments have structure (3)wherein subscripts e and f are both 0 and K together with R⁴¹ and R⁴² is—C(═O)— and the remaining R³⁸—R⁴⁰ variable groups are as previouslydefined. Other preferred embodiments have structure (4) whereinsubscript f is 1 and L together with R⁴³ and R⁴⁴ is —C(═O)— and K, L,subscript g and R³⁸—R⁴² are as previously defined.

In more preferred embodiments A, or A₁ and A₂ in -A₁-A₂-, independentlyhave the structure of (3a) or (4a):

wherein subscript e or f is 0 or 1 and G and R³⁹—R⁴⁴ are as previouslydefined.

When an L_(SS) or L_(S) moiety is comprised of A or A, preferred A or A₁structures correspond to those shown for (3), (3a), (4) and (4a) whereinR³⁸ is absent, G is a basic unit (BU) and the N-terminal nitrogen isincorporated into a M¹ or M² moiety as the imine nitrogen of thatmoiety's ring system or is incorporated into a M³ moiety as the amidenitrogen of the succinic acid amide.

In other more preferred embodiments A or A₁ and A_(o) of A correspondindependently in structure to or are independently selected residues ofan alpha-amino, beta-amino or other amine-containing acid. When anL_(SS) or L_(S) moiety is comprised of A or A₁, preferred A or A₁moieties correspond in structure to or are residues of an alpha-amino,beta-amino or other amine-containing acid substituted with BU (i.e., isa diamino-containing acid), wherein the N-terminal nitrogen of theBU-substituted alpha-amino, beta-amino or other amine-containing acid,which is represented by A(BU) or A₁(BU), is incorporated into a M¹ or M²moiety as the imine nitrogen of that moiety's ring system or isincorporated into M³ as the amide nitrogen of the succinic acid amidemoiety.

In those embodiments, particularly preferred A(BU) or A₁(BU) have thestructure of (3) or (3a) wherein subscript e is 0 and G is BU or havethe structure of (4) or (4a) wherein subscript f is 1 and G is BU. Inembodiments wherein W, Y and D⁺ are in linear arrangement wherein A_(O)is present, particularly preferred amine-containing acids incorporatedas A(have the structure of NH₂—X¹—CO₂H wherein X¹ is an optionallysubstituted C₁-C₆-alkylene, including ε-amino-caproic acid andβ-amino-propionic acid.

In preferred embodiments where A, W and Y are in an orthogonalconfiguration in -L_(B)-L_(O)-D⁺ or L_(B)′-L_(O)-D⁺ have the structureof:

and other preferred embodiment where A, W and Y are in a linearconfiguration in -L_(B)-L_(O)-D⁺ or L_(B)′-L_(O)-D⁺ have the structureof:

wherein A is a single unit and A_(O) is present.

In more preferred embodiments E′ is O′, J/J′ is —NH—, R³⁴ is methyl,isopropyl or —CH(OH)CH₃ and R³⁵ is methyl, —(CH₂)₃NH(C═O)NH₂ or—(CH₂)₂CO₂H, R⁴⁵ is —CO₂H and R′, R⁸, R⁹, J, V, Z¹, Z² and Z³ are aspreviously defined for Formula 1A, 1B, 1D or Formula IA, IB or ID. Inmore preferred embodiments R⁸ and R⁹ are each hydrogen. In still othermore preferred embodiments E is O′, J/J′ is —NH—, V, Z¹, Z² and Z³ areeach —CH═. Also more preferred are those embodiments wherein L_(B)′ hasthe structure of a maleimide moiety (M¹) or wherein L_(B) has thestructure of a succinimide moiety (M²) or an succinic acid-amide (M³)moiety.

More preferred are those embodiments in which L_(B)′-A has the structuregiven above for any one of the M¹-A-, and more preferred -L_(B)-A-moieties have the structure given above for any one of the M²-A- orM³-A₁- moieties. In any one of those embodiments J/J′ is preferably—NH—.

In preferred embodiments in which W′, Y and D⁺ are in a orthogonalrelationship A_(O) is present and has the structure previously definedfor (3), (3a), (4) or (4a), wherein the wavy line to the carbonyl moietyof any one of the structure represents the point of attachment of A_(O)to J′ preferably through an amide functional group and wherein the wavyline to the amino moiety of either structure represents the point ofattachment to a carbonyl-containing functional group of L_(P) or-L_(P)(PEG)-, preferably forming an amide functional group; wherein thevariable groups are as previously defined for structures representing A,or A₁ and A₂ in -A₁-A₂-. In preferred embodiments L is absent (i.e.,subscript q is 0) and G is hydrogen, —CO₂H or —NH₂ or the side chain ofa naturally occurring amino acid such as aspartic acid, glutamic acid orlysine. In other preferred embodiments, L and K are carbon and R⁴¹, R⁴²,R⁴³ and R⁴⁴ in each occurrence is hydrogen. In other preferredembodiments R³⁸—R⁴⁴ in each occurrence is hydrogen. Other preferredembodiments have structure (3) wherein K is nitrogen and one of R⁴¹, R⁴²is absent and the other is hydrogen. Other preferred embodiments havestructure (4) wherein r is 1, K is nitrogen and one of R⁴¹, R⁴² isabsent and the other is hydrogen. In other preferred embodimentssubscripts p and q of structure (3) are 0 or subscripts q and r ofstructure (4) are 0. Other preferred embodiments have structure (3)wherein subscripts p and q are both 0 and K together with R⁴¹ and R⁴² is—C(═O)—. Other preferred embodiments have structure (4) whereinsubscript q is 1 and L together with R⁴³ and R⁴⁴ is —C(═O)—.

In more preferred embodiments A or A₁ and A_(o) of A correspondindependently in structure to or is a residue of an alpha-amino,beta-amino or other amine-containing acid. In other more preferredembodiments having an L_(SS) or L_(S) moiety that moiety is comprised ofA or A₁ with preferred structures corresponding to those shown for (3),(3a), (4) and (4a) wherein R³⁸ is absent, G is a basic unit (BU) and theN-terminal nitrogen is incorporated into a M¹ or M² moiety as the iminenitrogen of that moieties ring system or is incorporated into a M³moiety as the amide nitrogen of the succinic acid amide. Other preferredA or A₁ moieties for L_(SS) or L_(S) correspond in structure to orincorporate an alpha-amino, beta-amino or other amine-containing acidsubstituted with BU (i.e., is a diamino-containing acid), wherein theN-terminal nitrogen of the BU-substituted alpha-amino, beta-amino orother amine-containing acid, which is represented by A(BU) or A₁(BU), isincorporated into a M¹ or M² moiety as the imine nitrogen of thatmoiety's ring system or is incorporated into M³ as the amide nitrogen ofthe succinic acid amide moiety.

In embodiments comprised of where A, W′ and Y are in an orthogonalconfiguration in -L_(B)-L_(O)-D⁺ or L_(B)′-L_(O)-D⁺ wherein A_(O) ispresent, particularly preferred amine-containing acids that correspondto A_(O) incorporate the structure of NH₂—X¹—CO₂H wherein X¹ is anoptionally substituted C₁-C₆-alkylene, including ε-aminocaproic acid andβ-amino-propionic acid.

Particularly preferred are any one of the above L_(B)-containingembodiments wherein the targeting moiety bonded to L_(B) is an antibody.

1.3.1 Ligand Unit

In some embodiments of the invention, a Ligand Unit is present. TheLigand Unit (L-) is a targeting moeity that specifically binds to atargeted moiety. The Ligand Unit can specifically bind to a cellcomponent (a Cell Binding Agent) or to other targeted molecules ofinterest. The Ligand Unit acts to target and present the quaternizedtubulysin Drug Units to the particular target cell population with whichthe Ligand Unit interacts for selective release of D⁺ as a freetubulysin compound. Targeting agents include, but are not limited to,proteins, polypeptides and peptides. Suitable Ligand Units include thosefrom targeting agent such as antibodies, e.g., full-length antibodiesand antigen binding fragments thereof, interferons, lymphokines,hormones, growth factors and colony-stimulating factors, vitamins,nutrient-transport molecules (such as, but not limited to, transferrin),or any other cell binding molecule or substance. The Ligand Unit can be,for example, from non-antibody protein targeting agent. Alternatively,the targeting agent can be, for example, an antibody. Preferredtargeting agents are larger molecular weight proteins, e.g., CellBinding Agents having a molecular weight of at least about 80 Kd.

A targeting agent reacts with a Ligand Covalent Binding Unit precursorL_(B)′ to form L-L_(B)- wherein L is a Ligand Unit and L_(B) is LigandCovalent Binding Unit. The targeting agent has to have the requisitenumber of attachment sites to accommodate the drug-linker moieties eachcomprising a L_(B), whether they be naturally occurring or non-naturallyoccurring (e.g., engineered). For example, in order for the value of thesubscript p to be from 6 to 14, a targeting agent has to be capable offorming a bond to 6 to 14 drug-linker moieties. A targeting agent canform a bond to L_(B)′ in the Linker Unit of a Drug Linker compound via areactive or activatable heteroatom or a heteroatom-containing functionalgroup of the targeting agent. Reactive or activatable heteroatoms or aheteroatom-containing functional groups that may be present on atargeting agent include sulfur (in one embodiment, from a sulfhydrylgroup of a targeting agent), C═O or (in one embodiment, from a carbonyl,carboxyl or hydroxyl group of a targeting agent) and nitrogen (in oneembodiment, from a primary or secondary amino group of a targetingagent). Those heteroatoms can be present on the targeting agent in thetargeting agent's natural state, for example a naturally-occurringantibody, or can be introduced into the targeting agent via chemicalmodification or biological engineering.

In one embodiment, a targeting agent has a sulfhydryl group and theLigand Unit therefrom is attached to the Linker Unit via the sulfhydrylgroup's sulfur atom.

In another embodiment, the targeting agent has lysine residues that canreact with activated esters (such esters include, but are not limitedto, N-hydroxysuccinimide, pentafluorophenyl, and p-nitrophenyl esters)of L_(B)′ of the Linker Unit of a Drug Linker compound and thus form anamide bond between of the nitrogen atom of the Ligand Unit and the C═Ogroup of the Linker Unit.

In yet another aspect, the targeting agent has one or more lysineresidues that can be chemically modified to introduce one or moresulfhydryl groups. The Ligand Unit from that targeting agent is attachedto the Linker Unit via the introduced sulfhydryl group's sulfur atom.The reagents that can be used to modify lysines in that manner include,but are not limited to, N-succinimidyl S-acetylthioacetate (SATA) and2-iminothiolane hydrochloride (Traut's Reagent).

In another embodiment, the targeting agent can have one or morecarbohydrate groups that can be chemically modified to have one or moresulfhydryl groups. The Ligand Unit from that targeting agent is attachedto the Linker Unit via the introduced sulfhydryl group's sulfur atom

In yet another embodiment, the targeting agent can have one or morecarbohydrate groups that can be oxidized to provide an aldehyde (—CHO)group (see, e.g., Laguzza, et al., 1989, J. Med. Chem. 32(3):548-55).The corresponding aldehyde can then react with a L_(B)′ having anucleophillic nitrogen. Reactive sites on a L_(B)′ that can react with acarbonyl group on a targeting agent include, but are not limited to,hydrazine and hydroxylamine. Other protocols for the modification ofproteins for the attachment of drug linker moieties are described inColigan et al., Current Protocols in Protein Science, vol. 2, John Wiley& Sons (2002) (incorporated herein by reference).

A targeting agent forms a bond with the reactive group on L_(B)′ of aDrug Linker compound to form a LDC in which a drug linker moiety thereofis comprised a L_(B)-containing moiety. A variety of reactive groups areuseful and will depend on the nature of the desired Ligand Unit. Thereactive group can be a maleimide which is present on L_(B)′ (prior toattachment to L) and covalent attachment of L to L_(B) is accomplishedthrough a sulfhydryl group of the targeting agent to form athio-substituted succinimide. The sulfhydryl group can be present on thetargeting agent in the targeting agent's natural state, for example anaturally-occurring residue, or can be introduced into the targetingagent via chemical modification.

In still another embodiment, the targeting agent is an antibody and thesulfhydryl group is generated by reduction of an interchain disulfide.Accordingly, in some embodiments, the Linker Unit is conjugated to acysteine residue of the reduced interchain disulfides of the LigandUnit.

In yet another embodiment, the targeting agent is an antibody and thesulfhydryl group is chemically introduced into the antibody, for exampleby introduction of a cysteine residue. Accordingly, in some embodiments,the Linker Unit is conjugated to an introduced cysteine residue.

It has been observed for bioconjugates that the site of drug conjugationcan affect a number of parameters including ease of conjugation,drug-linker stability, effects on biophysical properties of theresulting bioconjugates, and in-vitro cytotoxicity. With respect todrug-linker stability, the site of conjugation of a drug-linker to aLigand Unit can affect the ability of the conjugated drug-linker moietyto undergo an elimination reaction and for the drug linker moiety to betransferred from the Ligand Unit of a bioconjugate to an alternativereactive thiol present in the milieu of the bioconjugate, such as, forexample, a reactive thiol in albumin, free cysteine, or glutathione whenin plasma. Such sites include, for example, the interchain disulfides aswell as select cysteine engineered sites. The Ligand-Drug Conjugatesdescribed herein can be conjugated to thiol residues at sites that areless susceptible to the elimination reaction (e.g., positions 239according to the EU index as set forth in Kabat) in addition to othersites.

When the conjugates comprise non-immunoreactive protein, polypeptide, orpeptide ligands instead of an antibody, useful non-immunoreactiveprotein, polypeptide, or peptide ligands include, but are not limitedto, transferrin, epidermal growth factors (“EGF”), bombesin, gastrin,gastrin-releasing peptide, platelet-derived growth factor, IL-2, IL-6,transforming growth factors (“TGF”), such as TGF-α and TGF-β, vacciniagrowth factor (“VGF”), insulin and insulin-like growth factors I and II,somatostatin, lectins and apoprotein from low density lipoprotein.

Particularly preferred targeting agents are antibodies, including intactantibodies. In fact, in any of the embodiments described herein, theLigand Unit can be an antibody. Useful polyclonal antibodies areheterogeneous populations of antibody molecules derived from the sera ofimmunized animals. Useful monoclonal antibodies are homogeneouspopulations of antibodies to a particular antigenic determinant (e.g., acancer cell antigen, a viral antigen, a microbial antigen, a protein, apeptide, a carbohydrate, a chemical, nucleic acid, or fragmentsthereof). A monoclonal antibody (mAb) to an antigen-of-interest can beprepared by using any technique known in the art which provides for theproduction of antibody molecules by continuous cell lines in culture.

Useful monoclonal antibodies include, but are not limited to, humanmonoclonal antibodies, humanized monoclonal antibodies, or chimerichuman-mouse (or other species) monoclonal antibodies. The antibodiesinclude full-length antibodies and antigen binding fragments thereof.Human monoclonal antibodies may be made by any of numerous techniquesknown in the art (e.g., Teng et al., 1983, Proc. Natl. Acad. Sci. USA.80:7308-7312; Kozbor et al., 1983, Immunology Today 4:72-79; and Olssonet al., 1982, Meth. Enzymol. 92:3-16).

The antibody can be a functionally active fragment, derivative or analogof an antibody that immunospecifically binds to target cells (e.g.,cancer cell antigens, viral antigens, or microbial antigens) or otherantibodies bound to tumor cells or matrix. In this regard, “functionallyactive” means that the fragment, derivative or analog is able toimmunospecifically binds to target cells. To determine which CDRsequences bind the antigen, synthetic peptides containing the CDRsequences can be used in binding assays with the antigen by any bindingassay method known in the art (e.g., the BIA core assay) (See, e.g.,Kabat et al., 1991. Sequences of Proteins of Immunological Interest,Fifth Edition, National Institute of Health, Bethesda, Md.; Kabat E etal., 1980, J. Immunology 125(3):961-969).

Other useful antibodies include fragments of antibodies such as, but notlimited to, F(ab′)₂ fragments, Fab fragments, Fvs, single chainantibodies, diabodies, tribodies, tetrabodies, scFv, scFv-FV, or anyother molecule with the same specificity as the antibody.

Additionally, recombinant antibodies, such as chimeric and humanizedmonoclonal antibodies, comprising both human and non-human portions,which can be made using standard recombinant DNA techniques, are usefulantibodies. A chimeric antibody is a molecule in which differentportions are derived from different animal species, such as for example,those having a variable region derived from a murine monoclonal andhuman immunoglobulin constant regions. (See, e.g., U.S. Pat. Nos.4,816,567; and 4,816,397, which are incorporated herein by reference intheir entirety.) Humanized antibodies are antibody molecules fromnon-human species having one or more complementarity determining regions(CDRs) from the non-human species and a framework region from a humanimmunoglobulin molecule. (See, e.g., U.S. Pat. No. 5,585,089, which isincorporated herein by reference in its entirety.) Such chimeric andhumanized monoclonal antibodies can be produced by recombinant DNAtechniques known in the art, for example using methods described inInternational Publication No. WO 87/02671; European Patent PublicationNo. 0 184 187; European Patent Publication No. 0 171 496; EuropeanPatent Publication No. 0 173 494; International Publication No. WO86/01533; U.S. Pat. No. 4,816,567; European Patent Publication No. 012023; Berter et al., 1988, Science 240:1041-1043; Liu el al., 1987, Proc.Natl. Acad. Sci. USA 84:3439-3443; Liu et al., 1987, J. Immunol.139:3521-3526; Sun et al., 1987. Proc. Natl. Acad. Sci. USA 84:214-218;Nishimura et al., 1987, Cancer. Res. 47:999-1005; Wood et al., 1985,Nature 314:446-449; and Shaw et al., 1988, J. Natl. Cancer Inst.80:1553-1559; Morrison, 1985. Science 229:1202-1207; Oi et al., 1986.BioTechniques 4:214; U.S. Pat. No. 5,225,539; Jones et al., 1986, Nature321:552-525; Verhoeyan et al., 1988, Science 239:1534; and Beidler etal., 1988, J. Immunol. 141:4053-4060; each of which is incorporatedherein by reference in its entirety.

Completely human antibodies are particularly desirable and can beproduced using transgenic mice that are incapable of expressingendogenous immunoglobulin heavy and light chains genes, but which canexpress human heavy and light chain genes.

Antibodies include analogs and derivatives that are either modified,i.e., by the covalent attachment of any type of molecule as long as suchcovalent attachment permits the antibody to substantially retain itsantigen binding immunospecificity. For example, but not by way oflimitation, derivatives and analogs of the antibodies include those thathave been further modified, e.g., by glycosylation, acetylation,PEGylation, phosphorylation, amidation, derivatization by knownprotecting/blocking groups, proteolytic cleavage, linkage to a cellularantibody unit or other protein, etc. Any of numerous chemicalmodifications can be carried out by known techniques including, but notlimited to, specific chemical cleavage, acetylation, formylation,metabolic synthesis in the presence of tunicamycin, etc. Additionally,the analog or derivative can contain one or more unnatural amino acids.

Antibodies can have modifications (e.g., substitutions, deletions oradditions) in amino acid residues that interact with Fc receptors. Inparticular, antibodies can have modifications in amino acid residuesidentified as involved in the interaction between the anti-Fc domain andthe FcRn receptor (see, e.g., International Publication No. WO 97/34631,which is incorporated herein by reference in its entirety).

Antibodies immunospecific for a cancer cell antigen can be obtainedcommercially or produced by any method known to one of skill in the artsuch as, e.g., chemical synthesis or recombinant expression techniques.The nucleotide sequence encoding antibodies immunospecific for a cancercell antigen can be obtained, e.g., from the GenBank database or adatabase like it, the literature publications, or by routine cloning andsequencing.

In a specific embodiment, known antibodies for the treatment of cancercan be used. Antibodies immunospecific for a cancer cell antigen can beobtained commercially or produced by any method known to one of skill inthe art such as, e.g., recombinant expression techniques. The nucleotidesequence encoding antibodies immunospecific for a cancer cell antigencan be obtained, e.g., from the GenBank database or a database like it,the literature publications, or by routine cloning and sequencing.

In another specific embodiment, antibodies for the treatment of anautoimmune disease are used in accordance with the compositions andmethods of the invention. Antibodies immunospecific for an antigen of acell that is responsible for producing autoimmune antibodies can beobtained from any organization (e.g., a university scientist or acompany) or produced by any method known to one of skill in the art suchas, e.g., chemical synthesis or recombinant expression techniques.

In certain embodiments, useful antibodies can bind to a receptor or areceptor complex expressed on an activated lymphocyte. The receptor orreceptor complex can comprise an immunoglobulin gene superfamily member,a TNF receptor superfamily member, an integrin, a cytokine receptor, achemokine receptor, a major histocompatibility protein, a lectin, or acomplement control protein.

In some aspects, the antibody will specifically bind CD19, CD20, CD30,CD33, CD70, alpha-v-beta-6, or Lewis Y antigen.

The antibody can be a humanized anti-CD33 antibody (US 2013/0309223incorporated by reference herein in its entirety and for all purposes),a humanized anti-Beta6 antibody (see, e.g., WO 2013/123152 incorporatedby reference herein in its entirety and for all purposes), a humanizedanti-Liv-1 antibody (see, e.g., US 2013/0259860 incorporated byreference herein in its entirety and for all purposes), or a humanizedAC10 antibody (see. e.g., U.S. Pat. No. 8,257,706 incorporated byreference herein in its entirety and for all purposes).

Exemplary attachment to the Ligand is via thioether linkages. Thethioether linkages can be via interchain disulfide bonds, introducedcysteines resides, and combinations thereof.

1.3.2 Parallel Connector Unit

A Ligand Drug Conjugate, and its Drug Linker compound precursor of thepresent invention, are comprised of a PEG Unit that is in parallelorientation with the quaternized tubulysin Drug Unit in order toinfluence the pharmacokinetics of the resulting LDC. The parallelorientation of the PEG unit is accomplished by the Parallel ConnectorUnit (L_(P)). For that purpose the Parallel Connector Unit arranges theLigand, PEG and Drug Units in a branched configuration. Accordingly, theParallel Connector Unit can be considered a scaffolding component havingattachment sites for other components of the Ligand-Drug Conjugate andDrug Linker compound

In order to act as a parallel connector, the L^(P) Unit is attached viathree attachment sites within the Linker Unit. One of the attachmentsites connects the L^(P) Unit to the PEG Unit. In one embodiment asecond attachment site connects the L^(P) Unit to a protease susceptibleCleavable Unit (W), which is the connected to a self-immolative SpacerUnit (Y). In another embodiment a second attachment site of L_(P)connects directly to a self-immolative Spacer Unit (Y) to which is alsoattached a glycosidase-susceptible Cleavable Unit (W′), or in suchinstances indirectly connects to Y through an intervening Stretcher Unit(A_(O)). A third attachment site attaches the L_(P) Unit to theremainder of the Linker Unit, which in a LDC is typically connected tothe Ligand Unit through another Stretcher Unit (A). The ParallelConnector Unit is a unit that is distinct from the PEG Unit and isattached thereto via the PEG Attachment Unit component of the PEG Unit.In other words, the Parallel Connector Unit is not a subunit of the PEGUnit.

For the Ligand-Drug Conjugates and intermediates thereof having morethan one drug per PEG Unit, attachment of the Parallel Connector Unit toW or Y can be through a Branching Unit (B) in place of A_(O). In all ofthese embodiments, the L_(P) unit can be considered a tri-functionalchemical moiety that is capable of covalently linking together threespaced chemical moieties. As will be appreciated, for selectIntermediate Compounds, a precursor to L_(P) is represented by L_(P)′and is not yet completely incorporated into a Linker Unit (e.g. ispending attachment to A. A_(O), B, W or Y, but has an optionallyprotected functional group for that attachment). As will also beappreciated, the term “tri-functional” is used to denote the threeattachment sites and not the number of functional groups present on anyL_(P), L_(P)′, or subunit thereof.

A Parallel Connector Unit can be prepared from one or more (typicallyfrom 1 to 5 or 1 to 4 or 1 to 3 or 1 or 2) natural or non-natural aminoacid(s), amino alcohol(s), amino aldehyde(s), or polyamine(s) or somecombination thereof.

It will be appreciated that when referring to the natural or non-naturalamino acid, amino alcohol, amino aldehyde, or polyamine as present in anLDC or Drug Linker compound of the present invention (whether they bepart of a L_(P) Unit or other component of the LDC or Drug Linkercompound described herein), the amino acid, amino alcohol, aminoaldehyde, or polyamines will exist in residual form. For example, inembodiments, wherein the Parallel Connector Unit is two amino acids, thetwo amino acids will exist as residues with a peptide bond between them.In embodiments where the Parallel connector unit is comprised of anamino alcohol, the amino alcohol will exist as a residue where, forexample, its amino group is bonded to another residue of the ParallelConnector Unit or another component of the LDC or Drug Linker compoundthrough a carbonyl-containing functional group of that otherresidue/component while its hydroxyl group is bonded as an ether to, oris bonded through a carbonyl-containing functional group, of yet anotherresidue of the Parallel Connector Unit or another component of the LDCor Drug Linker compound. In embodiments where the Parallel ConnectorUnit is comprised of an amino aldehyde, the amino aldehyde will exist asa residue where, for example, its amino group is bonded to anotherresidue of the Parallel Connector Unit or another component of the LDCor Drug Linker compound through a carbonyl-containing functional groupof that other residue/component while its aldehyde functional group isconverted to an imino functional group or through subsequent reductionto provide a nitrogen-carbon bond when bonded to an amino group of yetanother residue of the Parallel Connector Unit or another component ofthe LIX, or Drug Linker compound. An amino alcohol or amino aldehyde maybe derived from a natural or unnatural amino acid by reduction of itscarboxylic acid functional group to an aldehyde or an hydroxylfunctional group.

In some embodiments a Parallel Connector Unit or subunit thereof havingthe required tri-functionality is provided by an amino acid or otheramine-containing acid residue that has or can be substituted with afunctionalized side chain to provide the requisite three points ofattachment. For example, serine has three functional groups, i.e., acid,amino and hydroxyl functional groups and may be viewed as a combinedamino acid and amino alcohol residue for purposes of its incorporationinto a Parallel Connector Unit. Tyrosine also contains a hydroxyl group,in this instance in its phenolic side chain, and may also be viewsimilarly to serine for purposes of its incorporation as a trifunctionalcomponent of a Parallel Connector Unit.

In another example, when the three attachment sites of a ParallelConnector Unit or subunit thereof is provided by cysteine, its amino andcarboxylic acid group will exist in residual form in a manner previouslydiscussed for amino acids or amine-containing acids to provide two ofthe three requisite points of attachment while its thiol group willexist in residual form to provide the other requisite attachment pointIn some instances, the residual thiol group is in its oxidized form(i.e., —S(═O)— or —S(═O₂—) when bonded to another subunit of theParallel Connector Unit or to another component of the Linker Unit. Inyet another example, the alpha amino and carboxylic acid group of alysine will exist in residual form to provide two of the three requisitepoints of attachment for a Parallel Connector Unit while it epsilonamino group in its residual form provides the remaining point ofattachment. Histidine may also be viewed as an amino acid with two aminogroups, where the second amino group is the NH of theimidazole-containing side chain.

In another example, when the three attachment sites of a ParallelConnector unit is provided by aspartic or glutamic acid, the alpha aminoand C-terminal carboxylic acid functional groups of the amino acid intheir residual forms provide two of the three requisite points ofattachment, while its beta or gamma carboxylic acid functional group inits residual form provides the remaining of attachment. In thoseinstances when a naturally occurring amino acid is recited as a ParallelConnector Unit or subunit thereof, but does not naturally contain afunctionalized amino acid side chain, yet is required to be atrifunctional component of L_(P), it is understood that the amino acidstructure is modified to have an additional functional group besides itsamino and carboxylic acid functional groups when in residual form inorder to provide the requisite third point of attachment. For example,an amino acid having an aliphatic side chain may be substituted at acarbon of that side chain with a hydroxyl, amino, aldehyde, thiol,carboxylic acid group or other functional group or other moiety (e.g.,an aryl or arylalkyl substituted with any one of these functionalgroups) to provide an unnatural amino acid having the requisite threepoints of attachment. Such unnatural amino acids are incorporated into aParallel Connector Unit as described above for amino acids and residualforms of the introduced functional groups.

Similarly, when an amino aldehyde or amino alcohol is incorporated intoa Parallel Connecting Unit that amino aldehyde or amino alcohol willhave a third functional group to provide, along with its amino andaldehyde functional groups, the requisite three points of attachment. Inthose instances, an amino aldehyde or amino alcohol may correspond instructure to a natural amino acid that has a functionalized side chainor an unnatural amino acid having an functional group that wasintroduced into the side chain of a natural amino acid as describedabove in which a carboxylic acid of the natural or unnatural amino acidis reduced to an hydroxyl or aldehyde functional group.

An amino acid residue of L_(P) can be that of an alpha, beta, or gammaamino acid or other amine-containing acid compound and can be in its D-or L-isomer if it contains a chiral carbon to which is bonded a naturalor unnatural amino acid side chain that provides the remaining requisitepoint of attachment. When the Parallel Connector Unit is made up of morethan one natural or non-natural amino acid, amino alcohol, aminoaldehyde, or polyamine, the amino acids, amino alcohols, aminoaldehydes, polyamines or combinations thereof are linked together viacovalent bonds to form the Parallel Connector Unit.

The amino acid, amino alcohol, or amino aldehyde can be non-natural andcan be modified to have a functionalized side chain for attachment tocomponents of a Ligand Drug Conjugate or Drug Linker compound (asdescribed above for a residue of a Parallel Connector Unit), as the casemay be. Exemplary functionalized amino acids, amino alcohols, or aminoaldehydes include, for example, azido or alkyne functionalized aminoacids, amino alcohols, or amino aldehydes (e.g., amino acid, aminoalcohol, or amino aldehyde modified to have an azide group or alkynegroup for attachment using click chemistry).

Attachment within the Parallel Connector Unit or with the othercomponents of the conjugate (or linker) can be, for example, via amino,carboxyl, or other functionalities. Methods for the independentactivation and reaction of the functional groups present on an aminoacid—e.g., the amine portion, the carboxylic acid portion and the sidechain portion (whether, for example, an amino moiety, a hydroxyl group,another carboxylic acid, thiol, azide or alkyne) include those adaptableform peptide chemistry.

The Parallel Connector Unit can comprise 1 or more (typically from 1 to5 or 1 to 4 or 1 to 3 or 1 or 2) amino acids, optionally substitutedC₁₋₂₀ heteroalkylenes (preferably optionally substituted C₁₋₁₂heteroalkylene), optionally substituted C₃₋₈ heterocyclos, optionallysubstituted C₆₋₁₄ arylenes, optionally substituted C₃-C₈ carbocyclos, orcombinations thereof. In some embodiments, the Parallel Connector Unitcomprises no more than 2 or no more than one optionally substitutedC₁₋₂₀ heteroalkylene, optionally substituted C₃₋₈ heterocyclo,optionally substituted C₆₋₁₄ arylene, or optionally substituted C₃-C₈carbocyclo. Optional substituents include (═O), —X, —R, —OR, —SR, —NR₂,—NR₃, ═NR, —CX₃, —CN, —OCN, —SCN, —N═C═O, —NCS, —NO, —NO₂, ═N₂, —N₃,—NRC(═O)R, —C(═O)R, —C(═O)NR₂, —SO₃ ⁻, —SO₃H, —S(═O)₂R, —OS(═O)₂OR,—S(═O)₂NR, —S(═O)R, —OP(═O)(OR)₂, —P(═O)(OR)₂, —PO₃, —PO₃H₂, —AsO₂H₂,—C(═O)R, —C(═O)X, —C(═S)R, —CO₂R, —CO₂—, —C(═S)OR, —C(═O)SR, —C(═S)SR,—C(═O)NR₂, —C(═S)NR′, or —C(═NR)NR₂, where each X is independently ahalogen: —F, —Cl, —Br, or —I; and each R is independently —H, —C₁ C₂₀alkyl, —C₆ C₂₀ aryl, —C₃ C₁₄ heterocycle, a protecting group or aprodrug moiety. Preferred optional substituents are (═O), —X, —R, —OR,—SR, and —NR₂.

A Parallel Connector Unit can be represented by Formula AA:

wherein AA¹ is a subunit of L^(P) independently selected from an aminoacid, optionally substituted C₁₋₂₀ heteroalkylene (preferably optionallysubstituted C₁₋₁₂ heteroalkylene), optionally substituted C₃₋₈heterocyclo, optionally substituted C₆₋₁₄ arylene, or optionallysubstituted C₃-C₈ carbocyclo;

and subscript h is independently selected from 0 to 4; and the wavy lineindicates covalent attachment sites within the Ligand-Drug Conjugate orintermediate thereof. The optionally substituted heteroalkylene,heterocycle, arylene or carbocyclo will have functional groups forattachments between the subunits and within a Ligand-Drug Conjugate orintermediates thereof.

In some embodiments at least one instance of AA¹ is an amino acid. Thesubscript h can be 0, 1, 2, 3, or 4. In some embodiments, AA¹ is anamino acid and h is 0. In some embodiments, the Parallel Connector Unitis comprised of no more than 2 optionally substituted C₁₋₂₀heteroalkylenes, optionally substituted C₃₋₈ heterocyclos, optionallysubstituted C₆₋₁₄ arylenes, or optionally substituted C₃-C₈ carbocyclos.In some embodiments of formula AA, the Parallel Connector Unit iscomprised of no more than 1 optionally substituted C₁₋₂₀ heteroalkylene,optionally substituted C₃₋₈ heterocyclo, optionally substituted C₆₋₁₄arylene, or optionally substituted C₃-C₈ carbocyclo.

A Parallel Connector Unit or an amino acid subunit thereof can beindependently selected from a thiol-containing amino acid. The thiolcontaining amino acid can be, for example, cysteine, homocysteine, orpenicillamine in the D- or L-stereochemical configuration.

A Parallel Connector Unit or an amino acid subunit thereof can beindependently selected from the group consisting of the L- or D-isomersof the following amino acids: Alanine (including β-alanine), arginine,aspartic acid, asparagine, cysteine, histidine, glycine, glutamic acid,glutamine phenylalanine, lysine, leucine, methionine, serine, tyrosine,threonine, tryptophan, proline, omithine, penicillamine, β-alanine,aminoalkynoic acid, aminoalkanedioic acid, heterocyclo-carboxylic acid,citrulline, statine, diaminoalkanoic acid, and derivatives thereof.

Preferred amino acids include cysteine, homocysteine, penicillamine,ornithine, lysine, serine, threonine, glutamine, alanine, aspartic acid,glutamic acid, selenocysteine, proline, glycine, isoleucine, leucine,methionine, valine, and alanine.

Exemplary L_(P) or AA¹ subunits thereof include:

where R¹¹⁰ is

R¹¹¹ is independently selected from hydrogen, p-hydroxybenzyl, methyl,isopropyl, isobutyl, sec-butyl, —CH₂OH, —CH(OH)CH₃, —CH₂CH₂SCH₃,—CH₂CONH₂, —CH₂COOH, —CH₂CH₂CONH₂, —CH₂CH₂COOH, —(CH₂)₃NHC(═NH)NH₂,—(CH₂)₃NH₂, —(CH₂)₃NHCOCH₃, —(CH₂)₃NHCHO, —(CH₂)₄NHC(═NH)NH₂,—(CH₂)₄NH₂, —(CH₂)₄NHCOCH₃, —(CH₂)₄NHCHO, —(CH₂)₃NHCONH₂,—(CH₂)₄NHCONH₂, —CH₂CH₂CH(OH)CH₂NH₂, 2-pyridylmethyl-, 3-pyridylmethyl-,4-pyridylmethyl-,

wherein the asterisk indicates attachment to the carbon labeled x;

R¹⁰⁰ is independently selected from hydrogen or —C₁-C₃ alkyl (preferablyhydrogen or CH₃),

R¹³ is independently selected from the group consisting of —C₁-C₆alkylene-, —C₃-C₈carbocyclo-, -arylene-, —C₁-C₁₀ heteroalkylene-,—C₃-C₈heterocyclo-, —C₁-C₁₀alkylene-arylene-, -arylene-C₁-C₁₀alkylene-,—C₁-C₁₀alkylene-(C₃-C₈carbocyclo)-, —(C₃-C₈carbocyclo)-C₁-C₁₀alkylene-,—C₁-C₁₀alkylene-(C₃-C₈ heterocyclo)-, and —(C₃-C₈ heterocyclo)-C₁-C₁₀alkylene- (preferably —CH₂—CH₂—);

Y is

Y′ is —C(═O)—, —O—, —S—, —NH—, or —N(CH₃)—, and

the subscripts p, q, and d are integers independently selected from 0 to5; and the wavy line indicates covalent attachment within the compound,hydrogen, OH or a C₁₋₃ unsubstituted alkyl group, provided that at leastone of the wavy lines indicates a covalent attachment within thecompound. In some aspects, all of the wavy lines indicate covalentattachment within the compound (e.g., when L^(P) does not comprise anysubunits).

In one group of embodiments, L^(P) is a heterocyclic ring havingfunctional groups that can independently form covalent linkages to thenoted components (e.g., a triazole heterocyclic ring formed fromcyanuric chloride). In another group of embodiments, L^(P) is an alkanehaving attached functional groups as noted above. In still otherembodiments. L^(P) can be a nitrogen atom.

In some embodiments, L_(P) of -L_(P)(PEG)-, once assembled, has theformula denoted below:

wherein the wavy line indicates the attachment sites within theLigand-Drug Conjugate or intermediate thereof, R¹⁰⁰ is as previouslydefined, the asterisk indicates attachment to the carbon labeled x andthe wavy line indicates one of the three attachment sites; Y isindependently selected from N or CH. Y′ is independently selected fromNH, O, or S, and each subscript c is an integer independently selectedfrom 1 to 10, and preferably 1, 2, or 3.

In preferred embodiments, R¹¹⁰ is not

In some embodiments L^(P) or subunit thereof is a aminoalkanedioic acid,a diaminoalkanoic acid, a sulfur-substituted alkanedioic acid, asulfur-substituted aminoalkanoic acid, a diaminoalkanol, anaminoalkanediol, a hydroxyl substituted alkanedioic acid, a hydroxylsubstituted aminoalkanoic acid or a sulfur-substituted aminoalkanolresidue, optionally substituted, wherein the sulfur substituent is inreduced or oxidized form.

In some embodiments a Parallel Connector Unit or an amino acid subunitthereof has the formula of Formula A or Formula B:

wherein subscript v is an integer ranging from 1 to 4; subscript v′ isan integer ranging from 0 to 4; X^(LP) is provided by a natural orun-natural amino acid side chain or is selected from the groupconsisting of —O—, —NR^(LP)—, —S—, —S(═O)—, —S(═O)₂—, —C(═O)—,—C(═O)N(R^(LP))—, —N(R^(LP))C(═O)N(R^(LP))—, and—N(R^(LP))C(═NR^(LP))N(R^(LP))—, wherein each R^(LP) is independentlyselected from the group consisting of hydrogen and optionallysubstituted alkyl or two of R^(LP) together along with their interveningatoms define a heterocycloalkyl and any remaining R^(LP) are aspreviously defined; Ar is an arylene or heteroarylene, optionallysubstituted; each R^(E) and R^(F) is independently selected from thegroup consisting of —H, optionally substituted alkyl, optionallysubstituted aryl and optionally substituted heteroaryl, or R^(E) andR^(F) together with the same carbon to which they are attached, or R^(E)and R^(F) from adjacent carbons together with these carbons, defines aoptionally substituted cycloalkyl with any remaining R^(E) and R^(F)substituents as previously defined; and wherein the wavy lines indicatescovalent attachment of the Formula A or Formula B structure within theLDC structure.

In some embodiments -L^(P)(PEG)- has the structure of Formula A1 or A2:

wherein the variable groups are as defined in Formula A.

In some embodiments, L_(P) has the structure of Formula X^(P) isprovided by a natural or un-natural amino acid side chain.

In preferred embodiments of Formula A, Formula A1, Formula A2 or FormulaB, R^(E) and R^(F) are independently selected from the group consistingof —H. and —C₁-C₄ alkyl. In preferred embodiments of Formula A, FormulaA1 or Formula A2, X^(LP) is selected from the group consisting of —O—,—NH, —S— and —C(═O)—

In some embodiments, L_(P) or a subunit thereof is selected from thegroup consisting of lysine, glutamic acid, aspartic acid, cysteine,penicillamine, serine or threonine in D- or L-stereochemicalconfiguration.

In other embodiments, L_(P) or a subunit thereof is selected from thegroup consisting of lysine, glutamic acid, aspartic acid, cysteine, orpenicillamine in D- or L-stereochemical configuration.

In other embodiments, L_(P) or a subunit thereof is a thiol containingamino acid in the D- or L-stereochemical configuration. The thiolcontaining amino acid is preferably cysteine, homocysteine, orpenicillamine.

In other embodiments, L_(P) or a subunit thereof is selected from thegroup consisting of the following amino acids or amine-containing acids:arginine, aspartic acid, asparagine, cysteine, histidine, glutamic acid,glutamine phenylalanine, serine, tyrosine, threonine, tryptophan,ornithine, penicillamine, aminoalkanedioic acid, heterocyclo-carboxylicacid, citrulline, diaminoalkanoic acid, and derivatives thereof in theD- or L-stereochemical configuration.

In other embodiments, L_(P), or a subunit thereof, is selected from thegroup consisting of cysteine, homocysteine, penicillamine, ornithine,lysine, serine, threonine, glutamine, aspartic acid, glutamic acid andselenocysteine.

In other embodiments, L_(P) or L_(P)′, or a subunit thereof, is selectedfrom the group consisting of arginine and arginine derivatives thereof.Illustrative of examples of arginine and derivatives thereof include butare not limited to: arginine (Arg), N-alkyl-arginine, H-Arg(Me)-OH,H-Arg(NH₂)—OH, H-Arg(NO₂)—OH, H-Arg(Ac)₂—OH, H-Arg(Me)₂-OH(asymmetrical), H-Arg(Me)-OH (symmetrical),2-amino-4-(2′-hydroxyguanidino)-butyric acid (N-ω-hydroxy-nor-arginine)and homoarginine.

In other embodiments, L_(P) or L_(P)′, or a subunit thereof, is selectedfrom the group consisting of aspartic acid and derivatives thereof.Illustrative of examples of aspartic acid and derivatives thereofinclude but are not limited to: aspartic acid (Asp), N-alkyl-asparticacid, and H-Asp(O-tBu)-OH.

In other embodiments, L_(P) or a subunit thereof is selected from thegroup consisting of asparagine and derivatives thereof. Illustrative ofexamples of asparagine and derivatives thereof include but are notlimited to: asparagine (Asn), N-alkyl-asparagine, and iso-asparagine(H-Asp-NH₂).

In other embodiments. L_(P) or L_(P)′, or a subunit thereof, is selectedfrom the group consisting of glutamic acid and derivatives thereof.Illustrative of examples of glutamic acid and derivatives thereofinclude but are not limited to: glutamic acid (Glu), N-alkyl-glutamicacid, H-Glu(OtBu)-OH, H-γ-hydroxy-Glu-OH, H-γ-methylene-Glu-OH,H-γ-carboxy-[Glu(O-tBu)]₂—OH, and pyroglutamic acid.

In other embodiments, L_(P) or L_(P)′, or a subunit thereof, is selectedfrom the group consisting of glutamine and derivatives thereof.Illustrative of examples of glutamine and derivatives thereof includebut are not limited to: glutamine (Gln), N-alkyl-glutamine, isoglutamine(H-Glu-NH₂), H-Gln(Trt)-OH, and H-Gln(isopropyl)-OH.

In other embodiments, L_(P) or L_(P)′, or a subunit thereof, is selectedfrom the group consisting of lysine and derivatives thereof.Illustrative of examples of lysine and derivatives thereof include butare not limited to: lysine (Lys), N-alkyl-lysine, H-Lys(Boc)-OH,H-Lys(Ac)—OH, H-Lys(Formyl)-OH, H-Lys(Me)₂-OH, H-Lys(nicotinoyl)-OH,H-Lys(Me)₃-OH, H-trans-4,5-dehydro-Lys-OH, H-Lys(Alloc)-OH, H—H-δ-hydroxy-Lys-OH, H-δ-hydroxy-Lys(Boc)-OH, H-Lys(acetamidoyl)-OH, andH-Lys(isopropyl)-OH.

In other embodiments, L_(P) or L_(P)′, or a subunit thereof, is selectedfrom the group consisting of serine and derivatives thereof.Illustrative of examples of serine and derivatives thereof include butare not limited to: serine (Ser), N-alkyl-serine, H-Ser(O—Ac)—OH,H-Ser(O-t-Bu)-OH, H-Ser(O-Bzl)-OH, H-Ser(p-chloro-O-Bzl)-OH,H-β-(3,4-dihydroxyphenyl)-Ser-OH, H-β-(2-thienyl)-Ser-OH, isoserineN-alkyl-isoserine, and 3-phenylisoserine.

In other embodiments, L_(P) or L_(P)′, or a subunit thereof, is selectedfrom the group consisting of tyrosine and derivatives thereof.Illustrative of examples of tyrosine and derivatives thereof include butare not limited to: tyrosine (Tyr), N-alkyl-tyrosine,H-3,5-dinitro-Tyr-OH, H-3-amino-Tyr-OH, H-3,5-dibromo-Tyr-OH,H-3,5-diiodo-Tyr-OH, H-Tyr(OMe)-OH, H-Tyr(O-t-Bu)-OH, H-Tyr(O-Boc)-OH,H-Tyr(O-Bzl)-OH, H-Tyr(O-Et)-OH, H-3-iodo-Tyr-OH, and H-3-nitro-Tyr-OH.

In other embodiments, L_(P), L_(P)′, or a subunit thereof, is selectedfrom the group consisting of threonine and derivatives thereof.Illustrative of examples of threonine and derivatives thereof includebut are not limited to: threonine (Thr), N-alkyl-threonine,allothreonine, H-Thr(OAc)—OH, II-Thr(O-t-Bu)-OH, and H-Thr(OBzl)-OH.

In other embodiments, L_(P), L_(P)′, or a subunit thereof, is selectedfrom the group consisting of tryptophan and derivatives thereof.Illustrative of examples of tryptophan and derivatives thereof includebut are not limited to: tryptophan (Trp). N-alkyl-tryptophan,H-5-Me-Trp-OH, H-5-hydroxy-Trp-OH, H-4-Me-Trp-OH, H-α-Me-Trp-OH,H-Trp(Boc)-OH, H-Trp(Formyl)-OH, and H-Trp(Mesitylene-2-sulfonyl)-OH.

In other embodiments, L_(P), L_(P)′, or a subunit thereof, is selectedfrom the group consisting of ornithine and derivatives thereof.Illustrative of examples of ornithine and derivatives thereof includebut are not limited to: ornithine (Orn), N-alkyl-ornithine,H-Orn(Boc)-OH, H-Orn(Z)—OH, H-α-difluoro-Me-Orn-OH (Eflornitine), andH-Orn(Alloc)-OH.

In other embodiments. L_(P), L_(P)′, or a subunit thereof, is selectedfrom the group consisting of penicillamine and derivatives thereof.Illustrative of examples of penicillamine and derivatives thereofinclude but are not limited to: penicillamine, H-penicillamine(Acm)-OH(H-β,β-dimethylcys(Acm)-OH) and N-alkyl-penicillamine.

In other embodiments, L_(P), or a subunit thereof, is selected from thegroup consisting of aminoalkanedioic acid and derivatives thereof.Illustrative of examples of an aminoalkanedioic acid and derivativesthereof include but are not limited to: N-alkylaminoalkanedioic acid,2-aminohexanedioic acid, 2-aminoheptanedioic acid, 2-aminooctanedioicacid (H-Asu-OH).

In other embodiments, L_(P), or a subunit thereof, is selected from thegroup consisting of citrulline and derivatives thereof. Illustrative ofexamples of citrulline and derivatives thereof include but are notlimited to: citrulline (cit), N-alkyl-citrulline, thiocitrulline.S-methyl-thiocitrulline, and homocitrulline.

In other embodiments, L_(P), L_(P)′, or a subunit thereof, is selectedfrom the group consisting of diaminoalkanoic acid and derivativesthereof. Illustrative of examples of diaminoalkanoic acid (Dab) andderivatives thereof include but are not limited to:N-alkyl-diamino-alkanoic acids. N,N-dialkylamino-alkanoic acids,α,γ-diaminobutyric acid (H-Dab-OH). H-Dab(Alloc)-OH, H-Dab(Boc)-OH,H-Dab(Z)—OH, α,β-diaminopropionic acid and its side-chain protectedversions.

An exemplary L_(P) unit or subunit thereof of, lysine or cysteine orpenicillamine, is shown below. The wavy line indicates attachment sitesto PEG and of L_(P) of L_(P)(PEG)-within the Linker Unit. L- andD-isomers of the amino acids are suitable for use herein.

An exemplary Ligand-Drug Conjugate having lysine as the L_(P) unit isshown below wherein L_(B), A, A_(O), L, W, W′, Y, D⁺, PEG, subscripts aand p, and PEG are as described herein. L- and D-isomers of the aminoacids are suitable for use herein.

An exemplary Ligand-Drug Conjugate having cysteine or penicillamine asthe L^(P) unit is shown below wherein L_(B), A, A_(O), L, W, W′, Y, D⁺,PEG, subscripts a and p, and PEG are as described herein. L- andD-isomers isomers of the amino acids are suitable for use herein.

1.3.3 PEG Unit

The PEG Units as taught herein are designed to impart an appropriatelevel of hydrophobicity masking of hydrophobic quaternized tubulysinDrug Units and other hydrophobic components of the quaternizeddrug-linker moiety of a Ligand Drug Conjugate. For that reason, theincorporation of PEG Unit as taught herein is particularly suitable forquaternized tubulysin-linkers that otherwise would impart sufficienthydrophobicity to negatively impact the pharmacokinetics of theresultant conjugate as compared to the Ligand Unit's unconjugatedtargeting agent. Those poorer pharmokinetics include greater plasmaclearance, which can be attributed to the hydrophobicity of thetubulysin compound that is quaternized in the Ligand Drug Conjugate.Thus, Ligand Drug Conjugates having a quaternized tubulysin Drug Unitthat display significantly greater plasma clearance and correspondinglylower plasma exposure relative to the Ligand Unit's unconjugatedtargeting agent will be benefited by the present invention. Ligand-DrugConjugates of the present invention have those more favorablepharmokinetic properties due to the parallel orientation within ahydrophobic drug-linker moiety of a quaternized tubulysin Drug Unit anda PEG Unit whereby the negative impact of hydrophobicity of thequaternized Drug Unit, which may be further aggravated by otherhydrophobic components of the quaternized tubulysin drug-linker moiety,on plasma clearance is sufficiently reduced or eliminated (i.e.,hydrophobicity of a drug-linker moiety is masked).

Polydisperse PEGS, monodisperse PEGS and discrete PEGs can be used tomake the Compounds of the present invention. Polydisperse PEGs are aheterogeneous mixture of sizes and molecular weights whereasmonodisperse PEGs are typically purified from heterogeneous mixtures andare therefore provide a single chain length and molecular weight.Preferred PEG Units are discrete PEGs, compounds that are synthesized instep-wise fashion and not via a polymerization process. Discrete PEGsprovide a single molecule with defined and specified chain length.

The PEG Unit provided herein comprises one or multiple polyethyleneglycol chains. The polyethylene glycol chains can be linked together,for example, in a linear, branched or star shaped configuration.Typically, at least one of the PEG chains is derivitized at one end forcovalent attachment to the Parallel Connector Unit. Exemplaryattachments to the Parallel Connector Unit are by means ofnon-conditionally cleavable linkages or via conditionally cleavablelinkages. Exemplary attachments are via amide linkage, ether linkages,ester linkages, hydrazone linkages, oxime linkages, disulfide linkages,peptide linkages or triazole linkages. In some aspects, attachment toL_(P) is by means of a non-conditionally cleavable linkage. In someaspects, attachment to L_(P) is not via an ester linkage, hydrazonelinkage, oxime linkage, or disulfide linkage. In some aspects,attachment to L_(P) is not via a hydrazone linkage.

A conditionally cleavable linkage refers to a linkage that is notsubstantially sensitive to cleavage while circulating in the plasma butis sensitive to cleavage in an intracellular or intratumoralenvironment. A non-conditionally cleavable linkage is one that is notsubstantially sensitive to cleavage in any biological environment.Chemical hydrolysis of a hydrazone, reduction of a disulfide, andenzymatic cleavage of a peptide bond or glycosidic linkage are examplesof conditionally cleavable linkages.

The PEG Unit will be directly attached to the Ligand-Drug Conjugate (orIntermediate thereof) at the Parallel Connector Unit. The other terminus(or termini) of the PEG Unit will be free and untethered and may takethe form of a methoxy, carboxylic acid, alcohol or other suitablefunctional group. The methoxy, carboxylic acid, alcohol or othersuitable functional group acts as a cap for the terminal PEG subunit ofthe PEG Unit. By untethered, it is meant that the PEG Unit will not beattached at that untethered site to a Drug Unit, to a Ligand Unit, or toa linking component linking a Drug Unit and/or a Ligand Unit. For thoseembodiments wherein the PEG Unit comprises more than one PEG chain, themultiple PEG chains may be the same or different chemical moieties(e.g., PEGs of different molecular weight or number of subunits). Themultiple PEG chains are attached to the Parallel Connector Unit at asingle attachment site. The skilled artisan will understand that the PEGUnit in addition to comprising repeating polyethylene glycol subunitsmay also contain non-PEG material (e.g., to facilitate coupling ofmultiple PEG chains to each other or to facilitate coupling to theParallel Connector Unit). Non-PEG material refers to the atoms in thePEG Unit that are not part of the repeating —CH₂CH₂O-subunits. Inembodiments provided herein, the PEG Unit can comprise two monomeric PEGchains linked to each other via non-PEG elements. In other embodimentsprovided herein, the PEG Unit can comprise two linear PEG chainsattached to a central core that is attached to the Parallel ConnectorUnit (i.e., the PEG unit itself is branched).

There are a number of PEG attachment methods available to those skilledin the art, [see, e.g., Goodson, et al. (1990) Bio/Technology 8:343(PEGylation of interleukin-2 at its glycosylation site aftersite-directed mutagenesis); EP 0 401 384 (coupling PEG to G-CSF); Malik,et al., (1992) Exp. Hematol. 20:1028-1035 (PEGylation of GM-CSF usingtresyl chloride); ACT Pub. No. WO 90/12874 (PEGylation of erythropoietincontaining a recombinantly introduced cysteine residue using acysteine-specific mPEG derivative); U.S. Pat. No. 5,757,078 (PEGylationof EPO peptides); U.S. Pat. No. 5,672,662 (Poly(ethylene glycol) andrelated polymers monosubstituted with propionic or butanoic acids andfunctional derivatives thereof for biotechnical applications); U.S. Pat.No. 6,077,939 (PEGylation of an N-terminal .alpha.-carbon of a peptide);Veronese et al., (1985) Appl. Biochem. Bioechnol 11:141-142 (PEGylationof an N-terminal α-carbon of a peptide with PEG-nitrophenylcarbonate(“PEG-NPC”) or PEG-trichlorophenylcarbonate); and Veronese (2001)Biomaterials 22:405-417 (Review article on peptide and proteinPEGylation)].

For example, PEG may be covalently bound to amino acid residues via areactive group. Reactive groups are those to which an activated PEGmolecule may be bound (e.g., a free amino or carboxyl group). Forexample, N-terminal amino acid residues and lysine (K) residues have afree amino group; and C-terminal amino acid residues have a freecarboxyl group. Sulfhydryl groups (e.g., as found on cysteine residues)may also be used as a reactive group for attaching PEG. In addition,enzyme-assisted methods for introducing activated groups (e.g.,hydrazide, aldehyde, and aromatic-amino groups) specifically at theC-terminus of a polypeptide have been described (see Schwarz, et al.(1990) Methods Enzymol. 184:160; Rose, et al. (1991) Bioconjugate Chem.2:154; and Gaertner, et al. (1994) J. Biol. Chem. 269:72241.

In some embodiments, PEG molecules may be attached to amino groups usingmethoxylated PEG (“mPEG”) having different reactive moieties.Non-limiting examples of such reactive moieties include succinimidylsuccinate (SS), succinimidyl carbonate (SC), mPEG-imidate,para-nitrophenylcarbonate (NPC), succinimidyl propionate (SPA), andcyanuric chloride. Non-limiting examples of such mPEGs includemPEG-succinimidyl succinate (mPEG-SS), mPEG₂-succinimidyl succinate(mPEG₂-SS); mPEG-succinimidyl carbonate (mPEG-SC), mPEG₂-succinimidylcarbonate (mPEG₂-SC); mPEG-imidate, mPEG-para-nitrophenylcarbonate(mPEG-NPC), mPEG-imidate; mPEG₂-para-nitrophenylcarbonate (mPEG₂-NPC);mPEG-succinimidyl propionate (mPEG-SPA); mPEG₂-succinimidyl propionate(mPEG, -SPA): mPEG-N-hydroxy-succinimide (mPEG-NHS);mPEG₂-N-hydroxy-succinimide (mPEG₂-NHS); mPEG-cyanuric chloride;mPEG₂-cyanuric chloride; mPEG₂-Lysinol-NPC, and mPEG₂-Lys-NHS.

Generally, at least one of the PEG chains that make up the PEG Unit isfunctionalized so that it can attach to the Parallel Connector Unit.Functionalization can be, for example, via an amine, thiol, NHS ester,maleimide, alkyne, azide, carbonyl, or other functional group. The PEGUnit can further comprise non-PEG material (i.e., material not comprisedof —CH₂CH₂O—) to facilitate coupling to the Parallel Connector Unit orto facilitate coupling of two or more PEG chains.

A wide variety of polyethylene glycol (PEG) species can be used, andsubstantially any suitable reactive PEG reagent can be used. In someembodiments, the reactive PEG reagent will result in formation of acarbamate or amide bond upon attachment to L_(P). The following PEGreagents are useful in various embodiments: mPEG₂-NHS, mPEG₂-ALD,multi-Arm PEG, mPEG(MAL)₂, mPEG₂(MAL), mPEG-NH₂, mPEG-SPA, mPEG-SBA,mPEG-thioesters, mPEG-Double Esters, mPEG-BTC, mPEG-ButyrALD, mPEG-ACET,heterofunctional PEGs (NH₂-PEG-COOH, Boc-PEG-NHS, Fmoc-PEG-NHS,NHS-PEG-VS. NHS-PEG-MAL). PEG acrylates (ACRL-PEG-NHS),PEG-phospholipids (e.g., mPEG-DSPE), multiarmed PEGs of the SUNBRITE™series including the GL series of glycerin-based PEGs activated by achemistry chosen by those skilled in the art, any of the SUNBRITEactivated PEGs (including but not limited to carboxyl-PEGs, p-NP-PEGs,Tresyl-PEGs, aldehyde PEGs, acetal-PEGs, amino-PEGs, thiol-PEGs,maleimido-PEGs, hydroxyl-PEG-amine, amino-PEG-COOKhydroxyl-PEG-aldehyde, carboxylic anhydride type-PEG, functionalizedPEG-phospholipid, and other similar and/or suitable reactive PEGs asselected by those skilled in the art for their particular applicationand usage.

The addition of the PEG Unit may have two potential impacts upon thepharmacokinetics of the resulting Ligand-Drug Conjugate. The desiredimpact is the decrease in clearance (and consequent in increase inexposure) that arises from the reduction in non-specific interactionsinduced by the exposed hydrophobic elements of the drug-linker. Thesecond impact is undesired impact and is the decrease in volume and rateof distribution that may arise from the increase in the molecular weightof the Ligand-Drug Conjugate. Increasing the number of PEG subunitsincreases the hydrodynamic radius of a conjugate, resulting in decreaseddiffusivity. In turn, decreased diffusivity may diminish the ability ofthe Ligand-Drug Conjugate to penetrate into a tumor (Schmidt andWittrup. Mol. Cancer Ther. 2009:8:2861-2871). Because of these twocompeting pharmacokinetic effects, it is desirable to use a PEG that issufficiently large to decrease the LDC clearance thus increasing plasmaexposure, but not so large as to greatly diminish its diffusivity, whichmay reduce the ability of the Ligand-Drug Conjugate to reach theintended target cell population.

In one group of embodiments, the PEG Unit comprises at least 6 subunits,at least 7 subunits, at least 8 subunits, at least 9 subunits, at least10 subunits, at least 11 subunits, at least 12 subunits, at least 13subunits, at least 14 subunits, at least 15 subunits, at least 16subunits, at least 17 subunits, at least 18 subunits, at least 19subunits, at least subunits, at least 21 subunits, at least 22 subunits,at least 23 subunits, or at least 24 subunits. As used herein a subunitwhen referring to the PEG Unit refers to a polyethylene glycol subunithaving the formula:

In another group of embodiments, the PEG Unit comprises one or morelinear PEG chains each having at least 2 subunits, at least 3 subunits,at least 4 subunits, at least 5 subunits, at least 6 subunits, at least7 subunits, at least 8 subunits, at least 9 subunits, at least 10subunits, at least 11 subunits, at least 12 subunits, at least 13subunits, at least 14 subunits, at least 15 subunits, at least 16subunits, at least 17 subunits, at least 18 subunits, at least 19subunits, at least 20 subunits, at least 21 subunits, at least 22subunits, at least 23 subunits, or at least 24 subunits. In preferredembodiments, the PEG Unit comprises a combined total of at least 6subunits, at least 8, at least 10 subunits, or at least 12 subunits. Insome such embodiments, the PEG Unit comprises no more than a combinedtotal of about 72 subunits, preferably no more than a combined total ofabout 36 subunits.

In another group of embodiments, the PEG Unit is a derivitized linearsingle PEG chain having from 2 to 72, 2 to 60, 2 to 48, 2 to 36 or 2 to24 subunits, from 2 to 72, 2 to 60, 2 to 48, 2 to 36 or 2 to 24subunits, from 3 to 72, 3 to 60, 3 to 48, 3 to 36 or 3 to 24 subunits,from 3 to 72, 3 to 60, 3 to 48, 3 to 36 or 3 to 24 subunits, from 4 to72, 4 to 60, 4 to 48, 4 to 36 or 4 to 24 subunits, from 5 to 72, 5 to60, 5 to 48, 5 to 36 or 5 to 24 subunits.

Exemplary linear PEG Units that can be used in any of the embodimentsprovided herein are as follows:

wherein the wavy line indicates site of attachment to the ParallelConnector Unit, R^(PEG1) is a PEG Attachment Unit. R^(PEG2) is a PEGCapping Unit; R^(PEG3) is an PEG Coupling Unit (i.e., for couplingmultiple PEG subunit chains together), subscript n is independentlyselected from 2 to 72 (preferably from 4 to 72, more preferably from 6to 72, from 8 to 72, from 10 to 72, from 12 to 72 or from 6 to 24);subscript e is 2 to 5, each subscript n′ is independently selected from1 to 72.

In preferred embodiments, there are at least 6, preferably at least 8,at least 10, or at least 12 PEG subunits in the PEG Unit. In someembodiments, there are no more than 72 or 36 PEG subunits in the PEGUnit.

In other preferred embodiments, subscript n is 8 or about 8, 12 or about12, 24 or about 24.

The PEG Attachment Unit is part of the PEG Unit and acts to link the PEGUnit to the Parallel Connector Unit. In this regard, the ParallelConnector Unit has a functional group that forms a bond with the PEGUnit. Functional groups for attachment of the PEG Unit to the ParallelConnector Unit include sulfhydryl groups to form disulfide bonds orthioether bonds, aldehyde, ketone, or hydrazine groups to form hydrazonebonds, hydroxylamine to form oxime bonds, carboxylic or amino groups toform peptide bonds, carboxylic or hydroxy groups to form ester bonds,sulfonic acids to form sulfonamide bonds, alcohols to form carbamatebonds, and amines to form sulfonamide bonds or carbamate bonds or amidebonds. Accordingly, the PEG unit can be attached to the ParallelConnector Unit, for example, via disulfide, thioether, hydrazone, oxime,peptide, ester, sulfonamide, carbamate, or amide bonds Typically, thePEG Attachment Unit is a product of the cycloaddition, addition,addition/elimination or substitution reaction that occurs when attachingthe PEG Unit to the Parallel Connector Unit.

The PEG Coupling Unit is part of the PEG Unit and is non-PEG materialthat acts to connect two or more chains of repeating CH₂CH₂O— subunits.In exemplary embodiments, the PEG coupling Unit R²² is —C₁₋₁₀alkyl-C(O)—NH—, —C₁₋₁₀alkyl-NH—C(O)—, —C₂₋₁₀ alkyl-NH—, —C₂₋₁₀ alkyl-O—,—C₁₋₁₀ alkyl-S—, or —C₂₋₁₀ alkyl-NH—.

In exemplary embodiments, the PEG Attachment Unit R²⁰ is —C(O)—, —O—,—S—, —S(O)—, —NH—, —C(O)O—, —C(O)C₁₋₁₀alkyl, —C(O)C₁₋₁₀ alkyl-O—,—C(O)C₁₋₁₀alkyl-CO₂—, —C(O)C₁₋₁₀alkyl-NH—, —C(O)C₁₋₁₀alkyl-S—,—C(O)C₁₋₁₀alkyl-C(O)—NH—, —C(O)C₁₋₁₀alkyl-NH—C(O)—, —C₁₋₁₀alkyl,—C₁₋₁₀alkyl-O—, —C₁₋₁₀alkyl-CO₂—, —C₁₋₁₀alkyl-NH—, —C₁₋₁₀alkyl-S—,—C₁₋₁₀ alkyl-C(O)—NH—, —C₁₋₁₀alkyl-NH—C(O)—, —CH₂CH₂SO₂—C₁₋₁₀alkyl-,—CH₂C(O)—C₁₋₁₀ alkyl-, ═N—(O or N)—C₁₋₁₀alkyl-O—, ═N—(O orN)—C₁₋₁₀alkyl-NH—, ═N—(O or N)—C₁₋₁₀alkyl-CO₂—, ═N—(O orN)—C₁₋₁₀alkyl-S—,

wherein

each R²¹ is independently —C₁₋₁₀ alkyl, —C₂₋₁₀ alkyl-CO₂H, —C₂₋₁₀alkyl-OH, —C₂₋₁₀ alkyl-NH₂, C₂₋₁₀ alkyl-NH(C₁₋₃ alkyl), or C₂₋₁₀alkyl-N(C₁₋₃ alkyl)₂; and each R²² is independently —C₁₋₁₀alkyl-C(O)—NH—, —C₁₋₁₀ alkyl-NH—C(O)—, —C₂₋₁₀ alkyl-NH—, —C₂₋₁₀alkyl-O—, —C₁₋₁₀ alkyl-S—, or —C₂₋₁₀ alkyl-NH—.

In some embodiments, R²⁰ is —NH—, —C(═O)—, triazole-linked groups, or—S—, or maleimido-linked groups such as

wherein the wavy line indicates the site of attachment to the ParallelConnector Unit and the asterisk indicates the site of attachment withinthe PEG Unit. In some such aspects, R²¹ is C₁₋₁₀ alkyl, —C₂₋₁₀alkyl-CO₂H, —C₂₋₁₀ alkyl-OH, or —C₂₋₁₀ alkyl-NH₂.

Illustrative linear PEG Units that can be used in any of the embodimentsprovided herein are as follows:

wherein the wavy line indicates site of attachment to the ParallelConnector Unit, and each subunit n is independently selected from 4 to72, 6 to 72, 8 to 72, 10 to 72, 12 to 72, 6 to 24, or 8 to 24. In someaspects, n is about 8, about 12, or about 24.

As described herein, the PEG unit is selected such that it improvesclearance of the resultant Ligand-Drug Conjugate but does notsignificantly impact the ability of the Conjugate to penetrate into thetumor. In embodiments wherein the quaternized Drug Unit and —W—Y— or—Y(W′)— in the Linker Unit of a Ligand-Drug Conjugate has ahydrophobicity comparable to that of a maleimido glucuronide MMAEdrug-linker (as shown in the examples), the PEG Unit to be selected foruse will preferably have from 8 subunits to about 24 subunits, morepreferably about 12 subunits. In embodiments wherein the quaternizedDrug Unit and —W—Y— or —Y(W′)— in the Linker Unit of a Ligand DrugConjugate has a hydrophobicity greater than that of a maleimidoglucuronide MMAE drug-linker, a PEG unit with more subunits can beselected. The methodology shown in the examples section can be used toidentify the ideal number of subunits for a particular drug-linker.

It will be appreciated that when referring to PEG subunits, anddepending on context, the number of subunits can represent an averagenumber, e.g., when referring to a population of Ligand-Drug Conjugatesor Intermediate Compounds (e.g., Drug Linker compounds), and usingpolydisperse PEGs.

1.3.4 Quaternized Tubulysins

In one group of embodiments, the quaternized tubulysin Drug Unitincorporates or corresponds in structure to a tubulysin having atertiary amine at the N-terminus, wherein the nitrogen atom of thattertiary amine is in quaternized form.

In some embodiments, the quaternized Drug Unit is that of a tubulysinrepresented by the structure of Formula D_(G), D_(H) or D_(H)′ whereinthe indicated nitrogen (†) is the site of quaternization when suchcompounds are incorporated into an LDC or a Drug Linker compound as aquaternized drug unit (D⁺):

wherein the indicated nitrogen (†) is the site of quaternization whensuch a tubulysin compound is incorporated into an LDC or a Drug Linkercompound as a quaternized tubulysin drug unit (D⁺); the circlerepresents an 5-membered or 6-membered nitrogen-containing heteroaryl,wherein the indicated required substituents to that heteroaryl are in a1,3- or meta-relationship to each other with optional substitution atthe remaining positions; the curved dashed line represents optionalcyclization; the straight dashed line to R² represent an optional doublebond or optionally two instances of R² independently selected or adivalent O-linked moiety; R² is X^(A)—R^(2A), wherein R^(2A) ishydrogen, optionally substituted alkyl, saturated or unsaturated, or—C(═O)R^(B), wherein R^(B) is hydrogen, optionally substituted alkyl,saturated or unsaturated, optionally substituted alkenyl or optionallysubstituted aryl; X^(A) is —O—, —S—, —N(R^(2C))—, —CH₂—, —C(═O)—,—(C═O)N(R^(2C))- or —O(C═O)N(R^(2C))—, wherein R^(2C) is hydrogen oroptionally substituted alkyl, or R² is an monovalent O-linkedsubstituent, and the double bond to R² is absent, or R² is O and thedouble bond to R² is present; R³ is hydrogen or optionally substitutedalkyl; R⁴, R^(4A), R^(4B), R⁵ and R⁶ are optionally substituted alkyl,independently selected, or R^(4A) and R^(4B), along with the atoms towhich they are attached define an optionally substitutedheterocycloalkyl, as indicated by the curved dashed line between R^(4A)and R^(4B) and R⁴, R⁵ and R⁶ are as previously defined; one R⁷ ishydrogen or optionally substituted alkyl and the other R⁷ is optionallysubstituted arylalkyl, or optionally substituted heteroarylalkyl.

In other embodiments the quaternized drug is a tubulysin represented bystructure of Formula D_(G) wherein one R⁷ is hydrogen or optionallysubstituted alkyl, preferably hydrogen or C₁-C₄, and the other R⁷ is anindependently selected optionally substituted alkyl, preferably C₁-C₆alkyl substituted by optionally substituted phenyl or —CO₂H or an esterprodrug thereof; R^(4A) and R^(4B), along with the atoms to which theyare attached define an optionally substituted C₅-C₆ heterocycloalkyl;and the other variable groups are as previously defined.

In some embodiments of Formula D_(G), R² is X^(A)—R^(2A), wherein X^(A)is —O— and R^(2A) is —C(═O)R^(C), wherein R^(C) is hydrogen, optionallysubstituted alkyl, preferably, methyl, ethyl, vinyl or a branched alkylor R² is an monovalent O-linked substituent selected from the groupconsisting of esters.

In other embodiment of Formula D_(G), R² is X^(A)—R^(2A), wherein X^(A)is —O—; and R^(2A) is hydrogen or optionally substituted alkyl,saturated or unsaturated, or R² is a monovalent O-linked substituentselected from the group consisting of ethers.

In preferred embodiments, the quaternized Drug Unit is that of atubulysin represented by the structure of Formula D_(G)′:

wherein subscript m is 0 or 1, one R⁷ is hydrogen and the other R⁷ is anoptionally substituted arylalkyl, wherein the alkyl moiety issubstituted by —CO₂H or an ester thereof and the remaining variablegroups are as defined for Formula Dc.

In other preferred embodiments —N(R⁷)(R⁷) of Formula D_(G) is replacedby —N(R⁷)—CH(R¹⁰)(CH₂R¹¹) to define quaternized tubulysin drugs ofFormula D_(H)′:

wherein R¹⁰ is C₁-C₆ alkyl substituted with —CO₂H, or ester thereof, andR⁷ is hydrogen or a C₁-C₆ alkyl independently selected from R¹⁰, or R⁷and R¹⁰ together with the atoms to which they are attached define a 5 or6-membered heterocycle; and R¹¹ is aryl or 5- or 6-membered heteroaryl,optionally substituted with one or more, preferably 1 or 2, morepreferably 1, substituent(s) independently selected from the groupconsisting of halogen, lower alkyl, —OH and —O—C₁-C₆ alkyl, preferably—F, —CH₃, and —OCH₃; and the remaining variable groups are as definedfor Formula D_(H).

In still other aspects one R⁷ in —N(R⁷)(R⁷) in Formula D_(G), FormulaD_(G)′ or Formula D_(H) is hydrogen or C₁-C₆ alkyl, and the other R⁷ isan independently selected C₁-C₆ alkyl optionally substituted by —CO₂H oran ester thereof, or by an optionally substituted phenyl.

In some embodiments of Formula D_(G), Formula D_(G)′ or Formula D_(H)one R⁷ is hydrogen and the other R⁷ is an optionally substitutedarylalkyl having the structure of:

wherein R^(7B) is hydrogen or an O-linked substituent, preferablyhydrogen or —OH in the para position, and R^(8A) is hydrogen or loweralkyl, preferably methyl; and wherein the wavy line indicates the pointof attachment to the remainder of D_(G), D_(G)′ or D_(H).

In preferred embodiments of Formula D_(G), Formula D_(G)′ or FormulaD_(H), one R⁷ is hydrogen, and the other R⁷ is an optionally substitutedarylalkyl having the structure of

wherein R^(7B) is —H or —OH; and wherein the wavy line indicates thepoint of attachment to the remainder of D_(G) or D_(G)′.

In other embodiments of structure Formula D_(G), Formula D_(G)′ orFormula D_(H), one R⁷ is hydrogen or C₁-C₄ alkyl, preferably hydrogen ormethyl, more preferably hydrogen, and the other R⁷ is optionallysubstituted arylalkyl having the structure of one of:

wherein Z is an optionally substituted alkylene or an optionallysubstituted alkenylene, R^(7B) is hydrogen or an O-linked substituent,preferably hydrogen or —OH in the para position, R^(8A) is hydrogen orlower alkyl, preferably methyl, and subscript n is 0, 1 or 2, preferably0 or 1; and wherein the wavy line indicates the point of attachment tothe remainder of D_(G) or D_(H).

In still other embodiments of Formula D_(G). Formula D_(G)′ or FormulaD_(H), —N(R⁷)(R⁷) is —NH(C₁-C₆ alkyl) wherein the C₁-C₆ alkyl isoptionally substituted by —CO₂H or an ester thereof, or by an optionallysubstituted phenyl, with —N(R⁷)(R⁷) is selected from the groupconsisting of —NH(CH₃), —CH₂CH₂Ph. and —CH₂—CO₂H, —CH₂CH₂COH and—CH₂CH₂CH₂CO₂H preferred.

In some embodiments of structure D_(H)′, R⁷ and R¹⁰ together with theatoms to which they are attached define an optionally substituted 5 or6-membered heterocycle wherein —N(R⁷)—CH(R¹⁰)(CH₂R¹¹) has the structureof:

wherein the wavy line indicates the point of attachment to the remainderof D_(H)′.

Some preferred quaternized Drug Units are that of a tubulysinrepresented by Formula D_(H-1), wherein the indicated nitrogen (†) isthe site of quaternization when such a tubulysin compound isincorporated into an LDC or Drug Linker compound as a quaternized drugunit (D⁺):

wherein the circle represents an 5-membered or 6-memberednitrogen-heteroaryl wherein the indicated required substituents to thatheteroaryl are in a 1,3- or meta-relationship to each other withoptional substitution at the remaining positions; R^(2A) is hydrogen oroptionally substituted alkyl or R^(2A) along with the oxygen atom towhich it is attached defines an O-linked substituent other than —OH; R³is hydrogen or optionally substituted alkyl; R⁴, R^(4A), R^(4B), R⁵ andR⁶ are optionally substituted alkyl, independently selected; R^(7A) isoptionally substituted aryl or optionally substituted heteroaryl, R^(8A)is hydrogen or optionally substituted alkyl and subscript m is 0 or 1.

In some preferred embodiments of Formula D_(G), D_(G)′, D_(H), D_(H)′,or D_(H-1), R⁴ is methyl or ethyl, R³ is optionally substituted alkyland R⁵ and R⁶ are independently selected side chain residues of naturalhydrophobic amino acids and the remaining variable groups are asdefined.

In other preferred embodiments of Formula D_(H-1), R^(7A) is optionallysubstituted phenyl. In other preferred embodiment R^(8A) is methyl inthe (S)-configuration. In other preferred embodiments of D_(H), D_(H)′or D_(H-1), R^(2A) along with the oxygen atom to which it is attacheddefines an O-linked substituent other than —OH, more preferably anester, ether or an O-linked carbamate. In more preferred embodiments thecircle represents a 5-membered nitrogen-containing heteroarylene with adivalent oxazole or thiazole moiety particularly preferred. In otherpreferred embodiments R⁴ is methyl or R^(4A) and R^(4B) are methyl. Inother preferred embodiments R⁷ is optionally substituted arylalkyl,wherein aryl is phenyl and R^(7A) is optionally substituted phenyl.

In other embodiments of Formula D_(G), D_(G)′, D_(H), D_(H)′ or D_(H-1)the circle represents a 5-membered nitrogen heteroarylene, preferablyrepresented by the structure

wherein X^(B) is O, S, or N—R^(B) wherein R^(B) is hydrogen or loweralkyl. Preferably the quaternized drug is that of a tubulysinrepresented by structure Formula D_(G)′, D_(H), D_(H)′ or D_(H-1),wherein subscript m is 1. More preferred are tubulysins represented bystructure Formula D_(G)′, D_(H), D_(H)′ or D_(H-1), wherein subscript mis 1 and the circle represents an optionally substituted divalentthiazole moiety.

Other quaternized Drug Units are that of a tubulysin represented by thestructure of Formula D_(I):

wherein the indicated nitrogen (†) is the site of quaternization whensuch a tubulysin compound corresponds to or is incorporated into an LDCor a Drug Linker compound as a quaternized drug unit (D⁺); the curveddashed lines indicate optional cyclizations; R^(2A) is hydrogen oroptionally substituted alkyl, or R^(2A) along with the oxygen atom towhich it is attached defines an O-linked substituent other than —OH, orR^(2A) is absent when R⁶ is bonded to that oxygen atom, as indicated bythe curved dash line between R⁶ and the oxygen atom, to define anoxygen-containing heterocycloalkyl; the circled Ar represents a5-membered nitrogen-heteroarylene, wherein the indicated requiredsubstituents to that heteroarylene are in a 1,3-relationship with eachother with optional substitution at the remaining positions; R³ ishydrogen or optionally substituted alkyl; R⁴, R⁵ and R⁶ are optionallysubstituted alkyl, independently selected, or R⁶ is bonded to the oxygenatom of the —OR^(2A) moiety in which R^(2A) is absent and R⁴ and R⁵ areas previously defined; R^(4a) is hydrogen or optionally substitutedalkyl and R^(4B) is optionally substituted alkyl, or both together withthe nitrogen to which they are attached, as indicated by the curveddotted line between R^(4A) and R^(4B), define a quaternized nitrogenheterocycloalkyl, optionally substituted; one R⁷ is hydrogen oroptionally substituted alkyl and the other R⁷ is optionally substitutedaralkyl or heteroaralkyl; wherein the wavy line indicates covalentbonding of the D⁺ structure to the remainder of the LDC structure.

In those embodiments the tubulysin compound preferably has the structureof Formula D_(I-1):

wherein subscript m is 0 or 1; Z is an optionally substituted alkyleneor an optionally substituted alkenylene; R^(7A) is optionallysubstituted aryl or optionally substituted heteroaryl; and the othervariable groups are as previously defined for Formula D_(I).

In preferred embodiments of Formula D_(I) the tubulysin compound has thestructure of Formula D_(I-2):

wherein R^(7A) is optionally substituted phenyl; R^(8A) is hydrogen ormethyl; and the other variable groups are as previously defined forFormula Dh.

In other preferred embodiments of Formula D_(I) the tubulysin compoundhas the structure of Formula D_(I-3):

wherein R⁵ and R⁶ are alkyl side chain residues of natural or unnaturalhydrophobic amino acids, independently selected; subscript u, indicatingthe number of R^(7B) substituents, is 0, 1, 2 or 3; each R^(7B), whenpresent, is an independently selected O-linked substituent; R^(8A) ishydrogen or optionally substituted alkyl; and the other variable groupsare as previously defined for Formula D_(I).

In more preferred embodiments of Formula D_(I) the tubulysin compoundhas the structure of Formula D_(I-4):

wherein the indicated nitrogen (†) is the site of quaternization whensuch a tubulysin compound corresponds to or is incorporated into an LDCor a Drug Linker compound as a quaternized drug unit (D⁺); R⁴ is methyl;subscript u is 0, 1 or 2; R³ is H, methyl, ethyl, propyl,—CH₂—OC(O)R^(3A), —CH₂CH(R^(3B))C(O)R^(3A) or —CH(R^(3B))C(O)NHR^(3A),wherein R^(3A) is C₁-C₆ alkyl and R^(3B) is H or C₁-C₆ alkyl,independently selected from R^(3A); R^(2A) along with the oxygen atom towhich it is attached is an O-linked substituent selected from the groupconsisting of —OCH₂OCH₂R^(2B), —OCH₂R^(2B), —OC(O)R^(2B),—CH₂OC(O)R^(2B), —OC(O)N(R^(2B))(R^(2C)), and—OCH₂C(O)N(R^(2B))(R^(2C)), wherein R^(2B) and R^(2C) are independentlyselected from the group consisting of H, C₁-C₆ alkyl and C₂-C₆ alkenyl;and each R^(7B), when present, independently is —OH or —OCH₃.

In other more preferred embodiments of Formula D_(I) the tubulysincompound has the structure of Formula D_(I-5):

wherein the indicated nitrogen (†) is the site of quaternization whensuch a tubulysin compound corresponds to or is incorporated into an LDCor a Drug Linker compound as a quaternized drug unit (D⁺); R^(2A) ishydrogen, an optionally substituted alkyl, saturated or unsaturated, orR² along with the oxygen atom to which it is attached defines anO-linked substituent other than —OH; R³ is optionally substituted C₁-C₆alkyl; R⁴ is methyl; R⁵ and R⁶ are alkyl side chain residues of naturalhydrophobic amino acids; and the —N(R^(7′))(R^(7′)) moiety is —NH(C₁-C₆alkyl) or —NH—N(C₁-C₆ alkyl)₂, wherein one and only one C₁-C₆ alkyl isoptionally substituted by —CO₂H, or an ester thereof, or by anoptionally substituted phenyl with the —N(R^(7′))(R^(7′)) moietypreferably selected from the group consisting of —NH(CH₃), —NHCH₂CH₂Ph,and —NHCH₂—CO₂H, —NHCH₂CH₂CO₂H and —NHCH₂CH₂CH₂CO₂H.

In any one of Formula D_(H), D_(H)′, D_(H-1), D_(I), D_(I-1), D_(I-2),D_(I-3), D_(I-4) and D_(I-5), preferably R^(2A) is —CH₂CH₃, —CH₂—CH═CH₂or —CH₂—C(CH₃)═CH₂.

In particularly preferred embodiments of Formula D the tubulysincompound has the structure of

wherein R^(2B) is —CH₃, —CH₂CH₃, —CH₂CH₂CH₃, —CH(CH₃)₂, —CH₂CH(CH₃)₂,—CH₂C(CH₃)₃; and the indicated nitrogen (†) is the site ofquaternization when such a tubulysin compound corresponds to or isincorporated into an LDC or a Drug Linker compound as a quaternized drugunit (D⁺).

In other particularly preferred embodiments of Formula D_(I) thetubulysin compound has the structure of

wherein R^(2B) is hydrogen, methyl or —OCH₃ (i.e., —OCH₂R^(2B) is amethyl, ethyl, or methoxymethyl ether substituent), or —OCH₂R^(2B) is—OCH₂CH═CH₂ or —OCH₂C(CH₃)═CH₂; and the indicated nitrogen (†) is thesite of quaternization when such a tubulysin compound corresponds to oris incorporated into an LDC or a Drug Linker compound as a quaternizeddrug unit (D⁺).

In other preferred embodiments of any one of Formula D_(I-1), D_(I-2),D_(I-2), D_(I-4) or D_(I-5): the thiazole core heterocyle

is replaced with

In some preferred embodiments of any one of Formula D_(H), D_(H)′,D_(H-1), D_(I), D_(I-1), D₁₋₂, D_(I-3), D_(I-4) and D_(I-5), R³ ismethyl or is —CH₂OC(═O)R^(3A), wherein R^(3A) is optionally substitutedalkyl. In other preferred embodiments of any one of those structures R³is —C(R^(3A))(R^(3A))C(═O)—X^(C), wherein X^(C) is —OR^(3B) or—N(R^(3C))(R^(3C)), wherein each R^(3A), R^(3B) and R^(3C) independentlyis hydrogen, optionally substituted alkyl or optionally substitutedcycloalkyl. Preferably R³ is —C(R^(3A))(R^(3A))C(═O)—N(R^(3C))(R^(3C)),with each R^(3A) hydrogen, one R^(3C) hydrogen and the other R^(3C)n-butyl or isopropyl more preferred.

In other preferred embodiments the tubulysin corresponding to orincorporated as D⁺ in an L E is a naturally occurring tubulysinincluding Tubulysin A, Tubulysin B, Tubulysin C, Tubulysin D, TubulysinE. Tubulysin F, Tubulysin G, Tubulysin H, Tubulysin I, Tubulysin U,Tubulysin V, Tubulysin W, Tubulysin X or Tubulysin Z, whose structuresare given by the following structure and variable group definitionswherein the indicated nitrogen (†) is the site of quaternization whensuch compounds are incorporated into an LDC as a quaternized drug unit(D⁺):

TABLE 1 Some Naturally Occurring Tubulysins Tubulysin R^(7B) R^(2A) R³ AOH C(═O)CH₃ CH₂O(C═O)i-Bu B OH C(═O)CH₃ CH₂O(C═O)n-Pr C OH C(═O)CH₃CH₂O(C═O)Et D H C(═O)CH₃ CH₂O(C═O)i-Bu E H C(═O)CH₃ CH₂O(C═O)n-Pr F HC(═O)CH₃ CH₂O(C═O)Et G OH C(═O)CH₃ CH₂O(C═O)CH═CH₂ H H C(═O)CH₃CH₂O(C═O)Me I OH C(═O)CH₃ CH₂O(C═O)Me U H C(═O)CH₃ H V H OH H Z OH OH H

In particularly preferred embodiments the quaternized tubulysin is thatof Tubulysin M.

1.4.1 Drug Linker Compounds L_(B)′-L_(O)-D⁺

In other preferred embodiments L_(B)′-L_(O)-D⁺ or L_(B)-L_(O)-D⁺ has thestructure of:

wherein R², R^(2A), R³, R⁴, R^(4A), R^(4B), R⁵, R⁶, R⁷, R^(7A) an R^(8A)are as described for tubulysin drugs in free form in structure D_(G)′,D_(H), D_(H)′, D_(H-1), D_(I), D_(I-1), D_(I-2), D_(I-3), D_(I-4) andD_(I-5), and L_(B), L_(A)′, L_(P), PEG, A, A_(O), V and Z³, andsubscripts m and p are as previously described for L_(B)- andL_(B)′-containing moieties described herein; E′ and J′ are independently—O—, —S— or —N(R³³), wherein R³³ is hydrogen or optionally substitutedalkyl; and R⁴⁵ is CO₂H or CH₂OH. In more preferred embodiments J′ is—NH—. In other preferred embodiments E′ is —O—.

More preferred are those embodiments where L_(B)′ is a maleimide (M¹)moiety or L_(B) is a succinimide (M²) or amide-acid (M³) moiety.

In other more preferred embodiments L_(B)′-L_(O)-D⁺ has the structureof:

wherein A, R^(2A), R³, R⁴⁵, R^(7B), R⁴⁵, and subscript u are aspreviously defined. In more preferred embodiments one or both of V, Z³are ═CH—.

In more preferred embodiments a L_(B)′-L_(O)-D⁺ or -L_(B)-L_(O)-D⁺moiety comprised of a quaternized tubulysin drug unit has the structureof:

wherein the wavy line indicates covalent bonding to a sulfhydryl groupof a Ligand Unit. In more preferred embodiments the carbohydrate moietycovalently attached to a self-immolative moeity of Y through a glycosidebond has its anomeric carbon in the β-configuration. In other morepreferred embodiments R⁴⁵ is —CH₂OH or —CO₂H.

In any one of the above embodiments for L_(B)-, L_(B)′-, M¹-, M²- orM³-containing moieties comprised of a quaternized tubulysin drug. R³ ispreferably methyl or R² is preferably acetate or subscript m ispreferably 1. Also, preferred for such L_(B)-, L_(B)′-, M¹-, M²- orM³-containing moieties are those wherein R³ is methyl, ethyl or propyland —OR^(2A) is —OC(O)CH₃, —OCH₃, —OCH₂CH₃, —OCH₂CH₂CH₃, —OCH₂CH═CH₂, or—OCH₂C(CH₃)═CH₂. In any one of those embodiments subscript u is 0 or is1 and R^(7B) is —OH

1.51 Treatment of Hyper-Proliferating Conditions

The Ligand-Drug Conjugates are useful for inhibiting the multiplicationof a tumor cell or cancer cell, causing apoptosis in a tumor or cancercell, or for treating cancer in a patient. The Ligand-Drug Conjugatescan be used accordingly in a variety of settings for the treatment ofcancers. The Ligand-Drug Conjugates can be used to deliver a drug to atumor cell or cancer cell. Without being bound by theory, in oneembodiment, the Ligand unit of a Ligand-Drug Conjugate binds to orassociates with a cell-surface cancer-cell or a tumor-cell-associatedantigen or receptor, and upon binding the Ligand-Drug Conjugate can betaken up (internalized) inside a tumor cell or cancer cell throughantigen- or receptor-mediated endocytosis or other internalizationmechanism. The antigen can be attached to a tumor cell or cancer cell orcan be an extracellular matrix protein associated with the tumor cell orcancer cell. Once inside the cell, via a enzymatic or non-enzymaticcleavable mechanism, depending upon the components of the linker system,the drug is released within the cell. In an alternative embodiment, theDrug or Drug unit is cleaved from the Ligand-Drug Conjugate within thevicinity of the tumor cell or cancer cell, and the Drug or Drug unitsubsequently penetrates the cell.

The Ligand-Drug Conjugates can provide conjugation-specific tumor orcancer drug targeting, thus reducing general toxicity of the drug.

In some embodiments, the Linker units stabilize the Ligand-DrugConjugates in blood, yet are capable of liberating drug once inside thecell.

In one embodiment, the Ligand unit binds to the tumor cell or cancercell.

In another embodiment, the Ligand unit binds to a tumor cell or cancercell antigen which is on the surface of the tumor cell or cancer cell.

In another embodiment, the Ligand unit binds to a tumor cell or cancercell antigen which is an extracellular matrix protein associated withthe tumor cell or cancer cell.

The specificity of the Ligand unit for a particular tumor cell or cancercell can be important for determining those tumors or cancers that aremost effectively treated. For example, a ligand drug conjugate having aBR96 Ligand Unit can be useful for treating antigen positive carcinomasincluding those of the lung, breast, colon, ovaries, and pancreas.Ligand-Drug Conjugates having an anti-CD30 or an anti-CD70 bindingLigand unit can be useful for treating hematologic malignancies.

Other particular types of cancers that can be treated with a ligand drugconjugates include, but are not limited to the following solid tumors,blood-borne cancers, acute and chronic leukemias, and lymphomas.

Solid tumors include but are not limited to fibrosarcoma, myxosarcoma,liposarcoma, chondrosarcoma, osteogenic sarcoma, chordoma, angiosarcoma,endotheliosarcoma, lymphangiosarcoma, lymphangioendotheliosarcoma,synovioma, mesothelioma, Ewing's tumor, leiomyosarcoma,rhabdomyosarcoma, colon cancer, colorectal cancer, kidney cancer,pancreatic cancer, bone cancer, breast cancer, ovarian cancer, prostatecancer, esophageal cancer, stomach cancer, oral cancer, nasal cancer,throat cancer, squamous cell carcinoma, basal cell carcinoma,adenocarcinoma, sweat gland carcinoma, sebaceous gland carcinoma,papillary carcinoma, papillary adenocarcinomas, cystadenocarcinoma,medullary carcinoma, bronchogenic carcinoma, renal cell carcinoma,hepatoma, bile duct carcinoma, choriocarcinoma, seminoma, embryonalcarcinoma, Wilms' tumor, cervical cancer, uterine cancer, testicularcancer, small cell lung carcinoma, bladder carcinoma, lung cancer,epithelial carcinoma, glioma, glioblastoma multiforme, astrocytoma,medulloblastoma, craniopharyngioma, ependymoma, pinealoma,hemangioblastoma, acoustic neuroma, oligodendroglioma, meningioma, skincancer, melanoma, neuroblastoma, and retinoblastoma.

Blood-borne cancers include but are not limited to acute lymphoblasticleukemia “ALL”, acute lymphoblastic B-cell leukemia, acute lymphoblasticT-cell leukemia, acute myeloblastic leukemia “AML”, acute promyelocyticleukemia “APL”, acute monoblastic leukemia, acute erythroleukemicleukemia, acute megakaryoblastic leukemia, acute myelomonocyticleukemia, acute nonlymphocyctic leukemia, acute undifferentiatedleukemia, chronic myelocytic leukemia “CML”, chronic lymphocyticleukemia “CLL”, hairy cell leukemia, and multiple myeloma.

Acute and chronic leukemias include but are not limited tolymphoblastic, myelogenous, lymphocytic, and myelocytic leukemias.

Lymphomas include but are not limited to Hodgkin's disease,non-Hodgkin's Lymphoma, Multiple myeloma, Waldenström'smacroglobulinemia, Heavy chain disease, and Polycythemia vera.

Cancers, including, but not limited to, a tumor, metastasis, or otherdiseases or disorders characterized by hyper-proliferating cells, can betreated or its progression inhibited by administration of an ADCcomposition.

In other embodiments, methods for treating cancer are provided,including administering to a patient in need thereof an effective amountof an LDC composition and a chemotherapeutic agent. In one embodimentthe cancer to be treated with a chemotherapeutic in combination with anLDC has not been found to be refractory to the chemotherapeutic agent.In another embodiment, the cancer to be treated with a chemotherapeuticin combination with an ADC is refractory to the chemotherapeutic agent.The LDC compositions can be administered to a patient that has alsoundergone surgery as treatment for the cancer.

In some embodiments, the patient also receives an additional treatment,such as radiation therapy. In a specific embodiment, the Ligand-DrugConjugate is administered concurrently with the chemotherapeutic agentor with radiation therapy. In another specific embodiment, thechemotherapeutic agent or radiation therapy is administered prior orsubsequent to administration of a ligand drug conjugate.

A chemotherapeutic agent can be administered over a series of sessions.Any one or a combination of the chemotherapeutic agents, such a standardof care chemotherapeutic agent(s), can be administered.

Additionally, methods of treatment of cancer with a Ligand DrugConjugate are provided as an alternative to chemotherapy or radiationtherapy where the chemotherapy or the radiation therapy has proven orcan prove too toxic, e.g., results in unacceptable or unbearable sideeffects, for the subject being treated. The patient being treated can,optionally, be treated with another cancer treatment such as surgery,radiation therapy or chemotherapy, depending on which treatment is foundto be acceptable or bearable.

1.6.1 Pharmaceutical Compositions

The present invention provides pharmaceutical compositions comprising anLDC composition described herein, or a pharmaceutically acceptable saltthereof, and one or more pharmaceutically acceptable excipients, or fromone to four pharmaceutically acceptable excipients, which is someembodiments includes a pharmaceutically acceptable carrier. Thepharmaceutical compositions can be in any form that allows for anAntibody Drug Conjugate as the LDC to be administered to a patient fortreatment of a disorder associated with expression of the antigen towhich the antibody of the ADC binds. For example, the pharmaceuticalcompositions can be in the form of a liquid or a lyophilized solid. Thepreferred route of administration is parenteral. Parenteraladministration includes subcutaneous injections, intravenous,intramuscular, and intrasternal injection or infusion techniques. Inpreferred embodiments, a pharmaceutical composition comprising an ADC isadministered intravenously in the form of a liquid solution. Preferablythe liquid solution is prepared from reconstitution of a solidpre-formulation from lyophilization of a liquid pre-formulationcomprising the ADC using a suitable pharmaceutically acceptable carrier.

Pharmaceutical compositions can be formulated so as to allow a compoundto be bioavailable upon administration of the composition to a patient.Such compositions can take the form of one or more dosage units, wherefor example, a lyophilized solid may provide a single dosage unit whenreconstituted as a solution or suspension on addition of a suitableliquid carrier.

Materials used in preparing the pharmaceutical compositions arepreferably non-toxic in the amounts used. It will be evident to those ofordinary skill in the art that the optimal dosage of the activeingredient(s) in the pharmaceutical composition will depend on a varietyof factors. Relevant factors include, without limitation, the type ofanimal (e.g., human), the particular form of the pharmaceuticalcomposition, the manner of administration, and the LDC compositionemployed.

The pharmaceutical composition can be, for example, in the form of aliquid. The liquid can be useful for delivery by injection. In acomposition for administration by injection, one or more of asurfactant, preservative, wetting agent, dispersing agent, suspendingagent, buffer, stabilizer and isotonic agent can also be included.

The liquid compositions, whether they are solutions, suspensions orother like form, can also include one or more of the following: sterilediluents such as water for injection, saline solution, preferablyphysiological saline, Ringer's solution, isotonic sodium chloride, fixedoils such as synthetic mono or digylcerides which can serve as thesolvent or suspending medium, polyethylene glycols, glycerin,cyclodextrin, propylene glycol or other solvents; antibacterial agentssuch as benzyl alcohol or methyl paraben; antioxidants such as ascorbicacid or sodium bisulfite; chelating agents such asethylenediaminetetraaectic acid; buffers such as amino acids, acetates,citrates or phosphates; detergents, such as nonionic surfactants,polyols; and agents for the adjustment of tonicity such as sodiumchloride or dextrose. A parenteral composition can be enclosed inampoule, a disposable syringe or a multiple-dose vial made of glass,plastic or other material. Physiological saline is an exemplaryadjuvant. An injectable pharmaceutical composition is preferablysterile.

The amount of the conjugate that is effective in the treatment of aparticular disorder or condition will depend on the nature of thedisorder or condition, and can be determined by standard clinicaltechniques. In addition, in vitro or in vivo assays can optionally beemployed to help identify optimal dosage ranges. The precise dose to beemployed in the compositions will also depend on the route ofadministration, and the seriousness of the disease or disorder, andshould be decided according to the judgment of the practitioner and eachpatient's circumstances.

The pharmaceutical composition comprises an effective amount of an LDCcomposition such that a suitable dosage will be obtained foradministration to a subject in need thereof. Typically, this amount isat least about 0.01% by weight of the pharmaceutical composition.

For intravenous administration, the pharmaceutical composition cancomprise from about 0.01 to about 100 ng of an LDC composition per kg ofthe animal's body weight. In one aspect, the pharmaceutical compositioncan include from about 1 to about 100 mg of a ADC composition per kg ofthe animal's body weight. In another aspect, the amount administeredwill be in the range from about 0.1 to about 25 mg/Kg of body weight ofan ADC composition.

Generally, the dosage of an LDC composition administered to a patient istypically about 0.01 mg/Kg to about 100 mg/Kg of the subject's bodyweight. In some embodiments, the dosage administered to a patient isbetween about 0.01 mg/Kg to about 15 mg/Kg of the subject's body weight.In some embodiments, the dosage administered to a patient is betweenabout 0.1 mg/Kg and about 15 mg/Kg of the subject's body weight. In someembodiments, the dosage administered to a patient is between about 0.1mg/Kg and about 20 mg/kg of the subject's body weight. In otherembodiments, the dosage administered is between about 0.1 mg/Kg to about5 mg/Kg or about 0.1 mg/Kg to about 10 mg/Kg of the subject's bodyweight. In other embodiments, the dosage administered is between about 1mg/Kg to about 15 mg/Kg of the subject's body weight. In otherembodiments, the dosage administered is between about 1 mg/Kg to about10 mg/Kg of the subject's body weight. In some embodiments, the dosageadministered is between about 0.1 to 4 mg/Kg, preferably 0.1 to 3.2mg/Kg, or more preferably 0.1 to 2.7 mg/Kg of the subject's body weightover a treatment cycle.

An LDC can be administered by any convenient route, for example byinfusion or bolus injection, by absorption through epithelial ormucocutaneous linings (e.g., oral mucosa, rectal and intestinal mucosa).Administration can be systemic or local. Various delivery systems areknown, e.g., encapsulation in liposomes, microparticles, microcapsules,capsules, and can be used to administer a compound. In certainembodiments, more than one compounds or composition is administered to apatient.

In an embodiment, the conjugates are formulated in accordance withroutine procedures as a pharmaceutical composition adapted forintravenous administration to animals, particularly human beings.Typically, the carriers or vehicles for intravenous administration aresterile isotonic aqueous buffer solutions. Where necessary, thecompositions can also include a solubilizing agent. Compositions forintravenous administration can optionally comprise a local anestheticsuch as lignocaine to ease pain at the site of the injection. Generally,the ingredients are supplied either separately or mixed together in unitdosage form, for example, as a dry lyophilized powder or water freeconcentrate in a hermetically sealed container such as an ampoule orsachet indicating the quantity of active agent. Where a conjugate is tobe administered by infusion, it can be dispensed, for example, with aninfusion bottle containing sterile pharmaceutical grade water or saline.Where the conjugate is administered by injection, an ampoule of sterilewater for injection or saline can be provided so that the ingredientscan be mixed prior to administration.

The pharmaceutical compositions are generally formulated as sterile,substantially isotonic and in full compliance with all GoodManufacturing Practice (GMP) regulations of the U.S. Food and DrugAdministration.

1.71 Numbered Embodiments

The following numbered embodiments further describe the inventionwithout limiting thereto.

1. A Ligand Drug Conjugate composition, wherein the composition isrepresented by the structure of Formula 1:

preferably in pharmaceutically acceptable salt form, wherein L is aLigand Unit; L_(B) is a Ligand Covalent Binding Unit; L_(P) is aParallel Connector Unit; PEG is a Polyethylene Glycol Unit; subscripts aand b independently are 0 or 1; subscript n is 1, 2, 3 or 4; A is afirst optional Stretcher Unit so that subscript a is 0 when A is absentor 1 when A is present and is optionally comprised of two, three or fourindependently selected subunits (A₁, A₂, A₃, A₄); B is an Branching Unitor a second optional Stretcher Unit (A_(O)) so that subscript b is 0when B is absent or 1 when B is present and is optionally comprised oftwo, three or four subunits independently of A, wherein subscript b is 1and B is a Branching when subscript n is 2, 3 or 4, or subscript b is 0,or subscript b is 1 so that B is A_(O), when subscript and is 1; Su is acarbohydrate moiety; —O′— represents an oxygen atom of an O-glycosidicbond cleavable by a glycosidase; -J′- represents a heteroatom,optionally substituted when nitrogen, preferably —NH—, or a nitrogenatom substituted by an optionally substituted alkyl, or an optionallysubstituted (heteroaryl)arylalkyl, from a functional group of B, when Bis present, or from Le, when B is absent; V, Z¹, Z² and Z³ are ═N— or═C(R²⁴)—, wherein R²⁴ is hydrogen or alkyl, alkenyl or alkynyl,optionally substituted, or halogen, —NO₂, —CN or other electronwithdrawing group, or —OCH₃ or other electron donating group, —O′-Su, or—C(R⁸)(R⁹)-D⁺, wherein at least at least two of V, Z¹, Z² and Z³ are═C(R²⁴)—, provided, one any only one R²⁴ is —C(R⁸)(R⁹)-D⁺ so that—C(R⁸)(R⁹)-D⁺ is bonded to one of V, Z¹, Z², Z³ when that variable groupis ═C(R²⁴)— and one and only one other R²⁴ is so that —O′-Su is bondedto another one of V, Z¹, Z², Z³ when that variable group is ═C(R²⁴)—,and the —O′-Su and —C(R⁸)(R⁹)-D⁺ substituents are ortho or para to eachother; R⁸ and R⁹ independently are hydrogen, alkyl, alkenyl or alkynyl,optionally substituted, or aryl or heteroaryl, optionally substituted;R′ is hydrogen or is halogen, —NO₂, —CN or other electron withdrawinggroup; D⁺ is a quaternized tubulysin Drug Unit; subscript p is anaverage drug loading having a number ranging from 1 to 24; and whereinsaid glycosidase cleavage results in release of a tubulysin compound (D)from a Ligand Drug Conjugate compound of the composition.

2. The Ligand Drug Conjugate composition of embodiment 1 wherein -D⁺ isa quaternized tubulysin compound preferably having the structure of:

wherein the circle represents an 5-membered nitrogen-heteroarylene andwherein the indicated required substituents to that heteroarylene are ina 1,3-relationship with each other with optional substitution at theremaining positions; subscript m is 0 or 1; R^(2A) is hydrogen oroptionally substituted alkyl, or R^(2A) along with the oxygen atom towhich it is attached defines an O-linked substituent; R³ is hydrogen oroptionally substituted alkyl; R⁴, R⁵ and R⁶ are optionally substitutedalkyl; one R⁷ is an optionally substituted alkyl, an optionallysubstituted arylalkyl, optionally substituted heteroarylalkyl and theother R⁷ is hydrogen or an optionally substituted alkyl; and R^(8A) ishydrogen or is optionally substituted alkyl, wherein the wavy lineindicates covalent bonding of D⁺ to the remainder of the Ligand DrugConjugate structure and wherein each optionally substituted alkyl isindependently selected.

3. The Ligand Drug Conjugate composition of embodiment 2 wherein thecomposition is represented by the structure of one of Formula 2A-2F:

4. The Ligand Drug Conjugate composition of embodiment 3 wherein L is anantibody Ligand Unit, thereby defining an antibody drug conjugate (ADC),wherein the antibody Ligand Unit selectively binds, or preferentially iscapable of binding, to an accessible cell-surface antigen of targetedabnormal or other unwanted cells that is capable of cellularinternalization of bound ADC, wherein the antigen is preferentiallypresent on the abnormal or other unwanted cells in comparison to normalcells.

5. The Ligand Drug Conjugate composition of embodiment 3 wherein L is acognate ligand of an accessible cell-surface receptor targeting thatcell-surface receptor, wherein the targeted receptor on abnormal cellsor other unwanted cells is capable of cellular internalization of boundLDC, and wherein the receptor is preferentially present on the abnormalcells in comparison to normal cells.

6. The Ligand Drug Conjugate composition of embodiment 3 wherein L is anantibody Ligand Unit, thereby defining an antibody drug conjugate (ADC),wherein the antibody Ligand Unit selectively, or preferentially bindsto, an accessible cell-surface antigen of vascular epithelial cells inthe vicinity of abnormal cells or other unwanted cells, wherein saidantigen is preferably more abundant on said cells in comparison toepithelial cells in the periphery and is capable of cellularinternalization of bound ADC.

7. The Ligand Drug Conjugate composition of any one of embodiments 1 to6 wherein —O′-Su has the structure of Formula 3:

wherein the wavy line represents covalent bonding of O′ to the remainderof the LDC structure; and R⁴⁵ is —CH₂OH or —CO₂H.

8. The Ligand Drug Conjugate composition of embodiment 7 wherein thecomposition is represented by the structure of Formula 4:

wherein Ab is an antibody Ligand Unit; J′ is —N(R³³)—, wherein R³³ ishydrogen or methyl; V and Z³ independently are ═CH— or ═N—; R′ ishydrogen or an electron withdrawing group; R⁸ is hydrogen; R⁹ ishydrogen, optionally substituted C₁-C₆ alkyl or optionally substitutedphenyl; R⁴⁵ is —CO₂H; and subscript p is a number ranging from 1 to 24.

9. The Ligand Drug Conjugate composition of embodiment 1 wherein a is 1;and -L_(B)-A- of Formula 1 has the structure of:

wherein the —[C(R^(b1))(R^(b1))]_(q)—[HE]- moiety is A or A₁, wherein A₁is a subunit of A; A₂₋₄ are optional subunits of A; R is hydrogen orC₁-C₄ alkyl; R^(a1) is hydrogen, optionally substituted alkyl or a BasicUnit (BU); and R^(a2) is hydrogen or optionally substituted alkyl, orR^(a1) and R^(a2) together with the carbon atom to which they areattached define a substituted or unsubstituted nitrogen-containingheterocycloalkyl; HE is an optional Hydrolysis Enhancer (HE) Unit;subscript q is an integer ranging from 0 to 6; each R^(b1) independentlyis hydrogen, optionally substituted C₁-C₆ alkyl, optionally substitutedaryl or optionally substituted heteroaryl, or two R^(b1) together withthe carbon(s) to which they are attached comprise or preferably define asubstituted or unsubstituted C₃-C₆ cycloalkyl or one R^(b1) and HEtogether with the carbon to which they are attached define a substitutedor unsubstituted 5 or 6-membered cycloalkyl or a substituted orunsubstituted 5- or 6-membered heterocycloalkyl and the other R^(b1) ishydrogen, optionally substituted C₁-C₆ alkyl, optionally substitutedaryl or optionally substituted heteroaryl; BU has the structure of—[C(R¹)(R¹)]—[C(R²)(R²)]_(r)—N(R²²)(R²³), or an acid addition saltthereof, wherein subscript r is 0, 1, 2 or 3; each R¹ independently ishydrogen or lower alkyl or two R¹ together with the carbon to which theyare attached comprise, or preferably define, a substituted orunsubstituted C₃-C₆ cycloalkyl, and each R² independently is hydrogen,optionally substituted C₁-C₆ alkyl, optionally substituted aryl oroptionally substituted heteroaryl, or two R² together with the carbon(s)to which they are attached and any intervening carbons define asubstituted or unsubstituted C₃-C₆ cycloalkyl, or one R¹ and one R²together with the carbons to which they are attached and any interveningcarbons define a substituted or unsubstituted 5- or 6-memberedcycloalkyl and the remaining R¹ and R² are as defined; R²² and R²³independently are hydrogen or optionally substituted C₁-C₆ alkyl ortogether with the nitrogen to which they are attached define asubstituted or unsubstituted 5- or 6-membered heterocycloalkyl, or oneof R²², R²³ is hydrogen and the other is an acid labile protectinggroup; and wherein the dotted line is an optional double bond and thewavy line to the succinimide (double bond is absent) or maleimide ring(double bond is present) of L_(B) indicates covalent bonding of sulfurderived from a sulfhydryl group of a targeting moiety and the other wavyline indicates covalent bonding to the remainder of the Ligand DrugConjugate structure.

10. The Ligand Drug Conjugate composition of embodiment 1 whereinsubscript a is 1; and -L_(B)-A- of Formula 1 or a compound thereof hasthe structure of:

wherein the —[C(R^(b1))(R^(b1))]_(q)-[HE]- moiety is A or A₁, wherein A₁is a subunit of A; A₂₋₄ are optional subunits of A; R is hydrogen orC₁-C₄ alkyl; Rai is hydrogen, optionally substituted alkyl or a BasicUnit (BU); and R^(a2) is hydrogen or optionally substituted alkyl, orR^(a1) and R^(a2) together with the carbon atom to which they areattached defines a substituted or unsubstituted nitrogen-containingheterocycloalkyl; HE is an optional Hydrolysis Enhancer (HE) Unit;subscript q is an integer ranging from 0 to 6; each R^(b1) independentlyis hydrogen, optionally substituted C₁-C₆ alkyl, optionally substitutedaryl or optionally substituted heteroaryl, or two R^(b1) together withthe carbon(s) to which they are attached comprise, or preferably define,a substituted or unsubstituted C₃-C₆ cycloalkyl or one R^(b1) and HEtogether with the carbon to which they are attached define a substitutedor unsubstituted 5 or 6-membered cycloalkyl or a substituted orunsubstituted 5- or 6-membered heterocycloalkyl and the other R^(b1) ishydrogen, optionally substituted C₁-C₆ alkyl, optionally substitutedaryl or optionally substituted heteroaryl; BU has the structure of—[C(R¹)(R¹)]—[C(R²)(R²)]_(r)—N(R²²)(R²³), or an acid addition saltthereof, wherein subscript r is 0, 1, 2 or 3: each R¹ independently ishydrogen or lower alkyl or two R¹ together with the carbon to which theyare attached comprise, or preferably define, an a substituted orunsubstituted C₃-C₆ cycloalkyl, and each R² independently is hydrogen,optionally substituted C₁-C₆ alkyl, optionally substituted aryl oroptionally substituted heteroaryl, or two R² together with the carbon(s)to which they are attached and any intervening carbons define asubstituted or unsubstituted C₃-C₆ cycloalkyl, or one R¹ and one R²together with the carbons to which they are attached and any interveningcarbons define a substituted or unsubstituted 5- or 6-memberedcycloalkyl and the remaining R¹ and R² are as defined; R²² and R²³independently are hydrogen or optionally substituted C₁-C₆ alkyl ortogether with the nitrogen to which they are attached define asubstituted or unsubstituted 5- or 6-membered heterocycloalkyl, or oneof R²², R²³ is hydrogen and the other is an acid labile protectinggroup; and wherein the dotted line is an optional double bond and thewavy line to the succinimide (double bond is absent) or maleimide ring(double bond is present) of L_(B) indicates covalent bonding of sulfurderived from a sulfhydryl group of a targeting moiety and the other wavyline indicates covalent bonding to the remainder of the Ligand DrugConjugate structure.

11. The Ligand Drug Conjugate composition of embodiment 9 wherein-L_(B)-A- of Formula 1 has the structure of:

wherein subscript q is an integer ranging from 0 to 4.

12. The Ligand Drug Conjugate composition of embodiment 10 wherein-L_(B)-A- of Formula 1 or a compound thereof has the structure of:

or an acid addition salt thereof, wherein R²² and R²³ are each hydrogenor one of R²², R²³ is hydrogen and the other is an acid labile carbamateprotecting group; and subscript q is an integer ranging from 0 to 4.

13. The Ligand Drug Conjugate composition of embodiment 12 wherein-L_(B)-A- of Formula I has the structure of:

wherein X⁻ is chloride, acetate, trifluoroacetate or dihydrogenphosphate.

14. The Ligand Drug Conjugate composition of embodiment 12 wherein-L_(B)-A- of Formula 1 or a compound thereof has the structure of:

wherein X⁻ is the counter anion of an acid addition salt.

15. The Ligand Drug Conjugate composition of embodiment 9 wherein thecomposition is represented by the structure of Formula 6:

wherein Ab is an antibody Ligand Unit and S is a sulfur atom of theantibody Ligand Unit; the asterisk (*) designates chirality or absencethereof at the indicated carbon; A₂₋₄ are independently selectedoptional subunits of A, wherein —[C(R^(b1))(R^(b1))]_(q)—[HE]- is A₁when one or more such subunits of A are present; R is hydrogen; R′ ishydrogen or an electron withdrawing group; R^(a1) is hydrogen or BUwherein BU is a Basic Unit having the structure of —CH₂—N(R²²)(R²³), oran acid addition salt thereof, wherein R²² and R²³ independently arehydrogen, methyl or ethyl or both together with the nitrogen atom towhich they are attached comprise, or preferably define, a substituted orunsubstituted 5- or 6-membered heterocycloalkyl, or one of R²², R²³ ishydrogen and the other is an acid labile carbamate protecting group,R^(a2) is hydrogen; subscript q is an integer ranging from 0 to 5 whenHE is present or 1 to 5 when HE is absent; each R^(b1) independently ishydrogen or optionally substituted C₁-C₆ alkyl; HE is absent or is—C(═O)—; R⁴⁵ is —CO₂H; J′ is —NH—; V and Z³ are ═CH₂—; R⁸ is hydrogen;R⁹ is hydrogen or methyl; and subscript p is a number ranging from 1 to16.

16. The Ligand Drug Conjugate composition of embodiment 1 wherein LigandDrug Conjugate compounds of the composition are independentlyrepresented by the structures of Formula 9A or Formula 9B:

wherein Ab is an antibody Ligand Unit; S is a sulfur atom of theantibody Ligand Unit, A₂₋₄ are independently selected optional subunit-sof A, wherein —[C(R^(b1))(R^(b1))]_(q)—[HE]- is A₁ when one or more suchsubunit are present; R is hydrogen; R′ is hydrogen or an electronwithdrawing group; R^(a1) is —H or BU wherein BU is a Basic Unit havingthe structure of —CH₂—N(R²²)(R²³), or an acid addition salt thereof,wherein R²² and R²³ independently are hydrogen or methyl or bothtogether with the nitrogen atom to which they are attached define asubstituted or unsubstituted basic nitrogen-containing 5- or 6-memberedheterocycloalkyl, or one of R²², R²³ is hydrogen and the other is anacid labile protecting group; R^(a2) is hydrogen; subscript q is aninteger ranging from 0 to 5 when HE is present or from 1 to 5 when HE isabsent, each R^(b1) independently is hydrogen or optionally substitutedC₁-C₆ alkyl; HE is absent or is —C(═O)—; J′ is —O— or —NH—; R⁸ and R⁹are independently —H or optionally substituted alkyl or both togetheralong with the carbon atom to which they are attached define asubstituted or unsubstituted cycloalkyl; and subscript p′ is an integerranging from 1 to 24.

17. The Ligand Drug Conjugate composition of embodiment 16 whereinLigand Drug Conjugate compounds of the composition are independentlyrepresented by the structure of Formula 10A or Formula 10B:

wherein R is hydrogen; R′ is hydrogen or —NO₂; HE is —C(═O)—; R⁴⁵ is—CO₂H; J′ is —NH—; V and Z³ are each ═CH₂—; R⁸ is hydrogen; and R⁹ ishydrogen or methyl.

18. The Ligand Drug Conjugate composition of embodiment 15, 16 or 17wherein the indicated starred (*) carbon is predominantly in the sameabsolute configuration as the alpha carbon of an L-amino acid when thatindicated carbon is chiral.

19. The Ligand Drug Conjugate composition of any one of embodiments 1 to8 wherein A and A_(O), when present, or any one of embodiments 9 to 18,wherein each of A₂₋₄, when present, independently have the structure ofFormula 7 or Formula 8:

wherein the wavy lines indicated covalent attachment within theremainder of the Ligand Drug Conjugate structure, wherein K and Lindependently are C, N, O or S, provided that when K or L is O or S, R⁴¹and R⁴² to K or R⁴³ and R⁴⁴ to L are absent, and when K or L are N, oneof R⁴¹, R⁴² to K or one of R⁴², R⁴³ to L are absent, and provided thatno two adjacent L are independently selected as N. O, or S; whereinsubscripts e and f are independently selected integers that range from 0to 12, and subscript g is an integer ranging from 1 to 12: wherein O ishydrogen, optionally substituted C₁-C₆ alkyl, —OH, —OR^(PR), —CO₂H,CO₂R^(PR), wherein R^(PR) is a suitable protecting, —N(R^(PR))(R^(PR)),wherein R^(PR) are independently a protecting group or R^(PR) togetherform a suitable protecting group, or —N(R⁴⁵)(R⁴⁶), wherein one of R⁴⁵,R⁴⁶ is hydrogen or R^(PR), wherein R^(PR) is a suitable protectinggroup, and the other is hydrogen or optionally substituted C₁-C₆ alkyl;wherein R³⁸ is hydrogen or optionally substituted C₁-C₆ alkyl; R³⁹—R⁴⁴independently are hydrogen, optionally substituted C₁-C₆ alkyl,optionally substituted aryl, or optionally substituted heteroaryl, orboth R³⁹, R⁴⁰ together with the carbon to which they are attachedcomprise or preferentially define a substituted or unsubstituted C₃-C₆cycloalkyl, or R⁴¹, R⁴² together with K to which they are attached whenK is C, or R⁴³, R⁴⁴ together with L to which they are attached when L isa carbon atom comprise or preferentially define a substituted orunsubstituted C₃-C₆ cycloalkyl, or R⁴⁰ and R⁴¹, or R⁴⁰ and R⁴³, or R⁴¹and R⁴³ to together with the carbon atom or heteroatom to which they areattached and the atoms intervening between those carbon atoms and/orheteroatoms comprise or preferably define a substituted or unsubstituted5- or 6-membered cycloalkyl or a substituted or unsubstitutedheterocycloalkyl, provided that when K is O or S, R⁴¹ and R⁴² areabsent, when K is N, one of R⁴¹, R⁴² is absent, when L is O or S, R⁴³and R⁴⁴ are absent, and when L is N, one of R⁴³, R⁴⁴ is absent, orwherein A_(O) is an alpha-amino, beta-amino or another amine-containingacid residue.

20. The Ligand Drug Conjugate composition of any one of embodiments 1 to19 wherein the quaternized tubulysin Drug Unit (-D⁺) is a tubulysincompound preferably having the structure of:

wherein the curved dashed lines indicate optional cyclizations; R^(2A)is hydrogen or optionally substituted alkyl, or R^(2A) along with theoxygen atom to which it is attached defines an O-linked substituentother than —OH, or R^(2A) is absent when R⁶ is bonded to that oxygenatom, as indicated by the curved dash line between R⁶ and the oxygenatom, to define a substituted or unsubstituted substitutedoxygen-containing heterocycloalkyl; the circled Ar represents a5-membered nitrogen-heteroarylene, wherein the indicated requiredsubstituents to that heteroarylene are in a 1,3-relationship with eachother with optional substitution at the remaining positions; R³ ishydrogen or optionally substituted alkyl; R⁴, R⁵ and R⁶ are optionallysubstituted alkyl, independently selected, or R⁶ is bonded to the oxygenatom of the —OR^(2A) moiety in which R^(2A) is absent and R⁴ and R⁵ areas previously defined; R^(4a) is hydrogen or optionally substitutedalkyl and R^(4B) is optionally substituted alkyl, or both together withthe nitrogen to which they are attached, as indicated by the curveddotted line between R^(4A) and R^(4B), define a substituted orunsubstituted quaternized nitrogen heterocycloalkyl, one R⁷ is hydrogenor optionally substituted alkyl and the other R⁷ is optionallysubstituted aralkyl or heteroaralkyl; wherein the wavy line indicatescovalent bonding of the D⁺ structure to the remainder of the Ligand DrugConjugated structure.

21. The Ligand Drug Conjugate composition of embodiment 20 wherein thequaternized tubulysin Drug Unit (-D⁺) has the structure of:

wherein subscript m is 0 or 1; Z is an optionally substituted alkyleneor an optionally substituted alkenylene; and R^(7A) is optionallysubstituted aryl or optionally substituted heteroaryl.

22. The Ligand Drug Conjugate composition of embodiment 21 wherein thequaternized tubulysin Drug Unit (-D⁺) has the structure of:

wherein R^(7A) is optionally substituted phenyl and R⁸ is hydrogen ormethyl.

23. The Ligand Drug Conjugate composition of embodiment 21 wherein thequaternized tubulysin Drug Unit (-D⁺) has the structure of:

wherein R⁵ and R⁶ are alkyl side chain residues of natural or un-naturalhydrophobic amino acids, preferably of hydrophobic natural amino acids,independently selected; subscript u, indicating the number of R^(7B)substituents, is 0, 1, 2 or 3; each R^(7B), when present, is anindependently selected O-linked substituent; and R^(8A) is hydrogen oroptionally substituted alkyl.

24. The Ligand Drug Conjugate composition of embodiment 22 wherein thequaternized tubulysin Drug Unit (-D⁺) has the structure of:

wherein R⁴ is methyl; subscript u is 0, 1 or 2; R³ is H, methyl, ethyl,propyl, —CH₂—OC(O)R^(3A), —CH₂CH(R^(3B))C(O)R^(3A) or—CH(R^(3B))C(O)NHR^(3A), wherein R is C₁-C₆ alkyl and R^(3B) is H orC₁-C₆ alkyl, independently selected from R^(3A); R^(2A) along with theoxygen atom to which it is attached is an O-linked substituent selectedfrom the group consisting of —OCH₂OCH₂R^(2B), —OCH₂R^(2B), —OC(O)R^(2B),—CH₂OC(O)R^(2B), —OC(O)N(R^(2B))(R^(2C)), and—OCH₂C(O)N(R^(2B))(R^(2C)), wherein R^(2B) and R^(2C) are independentlyselected from the group consisting of H, C₁-C₆ alkyl and C₂-C₆ alkenyl;and each R^(7B), when present, independently is —OH or —OCH₃.

25. The Ligand Drug Conjugate composition of embodiment 20 wherein thequaternized tubulysin Drug Unit (-D⁺) has the structure of:

wherein R^(2A) is hydrogen, an optionally substituted alkyl, saturatedor unsaturated, or R² along with the oxygen atom to which it is attacheddefines an O-linked substituent other than —OH; R³ is optionallysubstituted C₁-C₆ alkyl; R⁴ is methyl; R⁵ and R⁶ are alkyl side chainresidues of a hydrophobic natural or unnatural amino acids, preferablyof natural hydrophobic amino acids; and the —N(R^(7′))(R^(7′)) moiety is—NH(C₁-C₆ alkyl), optionally substituted by —CO₂H or an ester thereof,or by an optionally substituted phenyl, or is —N(C₁-C₆ alkyl)₂, whereinone and only one C₁-C₆ alkyl is optionally substituted by —CO₂H, or anester thereof, or by an optionally substituted phenyl.

26. The Ligand Drug Conjugate composition of embodiment 25 wherein the—N(R^(7′))(R^(7′)) moiety is selected from the group consisting of—NH(CH₃), —NHCH₂CH₂Ph, and —NHCH₂—CO₂H, —NHCH₂CH₂CO₂H and—NHCH₂CH₂CH₂CO₂H.

27. The Ligand Drug Conjugate composition of any one of embodiments 21to 26 wherein R^(2A) is —CH₂CH₃.

28. The Ligand Drug Conjugate composition of any one of embodiments 21to 26 wherein R^(2A) is —CH₂—CH═CH₂.

29. The Ligand Drug Conjugate composition of embodiment 24 whereinR^(2A) is —CH₂CH₃, —CH₂—CH═CH₂ or —CH₂C(CH₃)═CH₂, R^(2B) is —CH₃, R³ is—CH₃ and subscript u is 0.

30. The Ligand Drug Conjugate composition of embodiment 24 whereinR^(2A) is —CH₂CH, or —CH₂—CH═CH₂, or —CH₂C(CH₃)═CH₂, R^(2B) is —CH₃, R³is —CH₃ and subscript u is 1, wherein R^(7B) is —OH.

31. The Ligand Drug Conjugate composition of embodiment 24 wherein thequaternized tubulysin Drug Unit (-D⁺) has the structure of:

wherein R^(2B) is —CH₃, —CH₂CH₃, —CH₂CH₂CH₃, —CH(CH₃)₂, —CH₂CH(CH₃)₂, or—CH₂C(CH₃)₃.

32. The Ligand Drug Conjugate composition of embodiment 24 wherein thequaternized tubulysin Drug Unit (-D⁺) has the structure of:

wherein R^(2B) is hydrogen, methyl or —OCH₃, or —OCH₂R^(2B) is—OCH₂CH═CH₂ or —OCH₂C(CH₃)═CH₂.

33. The Ligand Drug Conjugate composition of embodiment 24 wherein thequaternized tubulysin Drug Unit (-D⁺) is that of tubulysin M, for whichD⁺ has the structure of:

34. The Ligand Drug Conjugate composition of any one of embodiments 1 to33 wherein L_(P) is a aminoalkanedioic acid, a diaminoalkanoic acid, asulfur-substituted alkanedioic acid, a sulfur-substituted aminoalkanoicacid, a diaminoalkanol, an aminoalkanediol, a hydroxyl substitutedalkanedioic acid, a hydroxyl substituted aminoalkanoic acid or asulfur-substituted aminoalkanol residue, optionally substituted, whereinthe sulfur substituent is in reduced or oxidized form.

35. The Ligand Drug Conjugate composition of any one of embodiments 1 to33 wherein L_(P) is an amino acid residue of lysine, arginine,asparagine, glutamine, ornithine, citrulline, cysteine, homocysteine,penicillamine, threonine, serine, glutamic acid, aspartic acid,tyrosine, histidine or tryptophan, wherein the amino acid is in the D-or L-configuration.

36. The Ligand Drug Conjugate composition of embodiment 34 wherein theaminoalkanedioic acid, diaminoalkanoic acid, sulfur-substitutedaminoalkanoic acid or hydroxyl substituted aminoalkanoic acid residuehas the structure of Formula A or B:

wherein subscript v is an integer ranging from 1 to 4; subscript v is aninteger ranging from 0 to 4; X^(LP) is selected from the groupconsisting of —O—, —NR—, —S—, —S(═O)—, —S(═O)₂—, —C(═O)—,—C(═O)N(R^(LP))—, —N(R^(LP))C(═O)N(R^(LP))—, and—N(R^(LP))C(═NR^(LP))N(R^(LP))— wherein each R^(LP) is independentlyselected from the group consisting of hydrogen and optionallysubstituted alkyl or two of R^(LP) together along with their interveningatoms define an optionally substituted heterocycloalkyl and anyremaining R^(LP) are as previously defined; Ar is an arylene orheteroarylene, optionally substituted; each R^(E) and R^(F) isindependently selected from the group consisting of —H, optionallysubstituted alkyl, optionally substituted aryl and optionallysubstituted heteroaryl, or R^(E) and R^(F) together with the same carbonto which they are attached, or R^(E) and R^(F) from adjacent carbonstogether with these carbons define a substituted or unsubstitutedcycloalkyl, with any remaining R^(E) and R^(F) substituents aspreviously defined; and wherein the wavy lines indicates covalentattachment of the Formula A or Formula B structure within the LigandDrug Conjugate structure.

37. The Ligand Drug Conjugate composition of any one of embodiments 1 to16 wherein -L_(P)(PEG)- has the structure of Formula A1 or A2:

wherein X^(LP) is selected from the group consisting of —O—, —NH, —S—and —C(═O)—; R^(E) and R^(F) are independently selected from the groupconsisting of —H and —C₁₋₄ alkyl; and wherein the wavy line indicatescovalent attachment of Formula A1 or Formula A2 within the Ligand DrugConjugate structure.

38. The Ligand Drug Conjugate composition of embodiment 1 wherein thecomposition is represented by the structure(s) of:

wherein the curved dashed lines indicate optional cyclizations; Ab is anantibody Ligand Unit; S is a sulfur atom of the antibody Ligand Unit;the Ab-S— moiety is bonded to the carbon α or β to the indicated M³carboxylic acid; R^(2A) is hydrogen or optionally substituted alkyl, orR^(2A) along with the oxygen atom to which it is attached defines anO-linked substituent other than —OH, or R^(2A) is absent when R⁶ isbonded to that oxygen atom, as indicated by the curved dash line betweenR⁶ and the oxygen atom, to define a substituted or unsubstitutedoxygen-containing heterocycloalkyl; the circled Ar represents a5-membered nitrogen-heteroarylene, wherein the indicated requiredsubstituents to that heteroarylene are in a 1,3-relationship with eachother with optional substitution at the remaining positions; R³ ishydrogen or optionally substituted alkyl; R⁴, R⁵ and R⁶ are optionallysubstituted alkyl, independently selected, or R⁶ is bonded to the oxygenatom of the —OR^(2A) moiety in which R^(2A) is absent and R⁴ and R⁵ areas previously defined; R^(4a) is hydrogen or optionally substitutedalkyl and R^(4B) is optionally substituted alkyl, or both together withthe nitrogen to which they are attached define a substituted orunsubstituted nitrogen quaternized heterocycloalkyl as indicated by thecurved dashed line between R^(4A) and R^(4B); one R⁷ is hydrogen oroptionally substituted alkyl and the other R⁷ is optionally substitutedaralkyl or heteroaralkyl; and subscript p is a number ranging from 1 to16.

39. The Ligand Drug Conjugate composition of embodiment 38 wherein thecomposition is represented by the structure(s) of:

wherein subscript is 0 or 1; subscript p is a number ranging from 1 to8; Z is an optionally alkylene or an optionally substituted alkenylene;and R^(7A) is optionally substituted aryl or optionally substitutedheteroaryl.

40. The Ligand Drug Conjugate composition of embodiment 39 wherein thecomposition is represented by the structure(s) of:

wherein R³ is optionally substituted alkyl; R⁴ is methyl; R⁵ and R⁶ arealkyl side chain residues of natural or un-natural hydrophobic aminoacids, preferably of natural hydrophobic amino acids, independentlyselected; subscript p is a number ranging from 1 to 8; subscript u,indicating the number of R^(7B) substituents, is 0, 1, 2 or 3; whereineach R^(7B), when present, is an independently selected O-linkedsubstituent; and R^(8A) is hydrogen or optionally substituted alkyl.

41. The Ligand Drug Conjugate composition of embodiment 40) wherein thecomposition is represented by the structure(s) of:

wherein R⁴ is methyl, subscript a is 0, 1 or 2; R³ is H, methyl, ethyl,propyl, —CH₂—OC(O)R^(3A), —CH₃CH(R^(3B))C(O)R^(3A) or—CH(R^(3B))C(O)NHR^(3A), wherein R^(3A) is C₁-C₆ alkyl and R^(3B) is Hor C₁-C₆ alkyl, independently selected from R^(3A); R^(2A) along withthe oxygen atom to which it is attached is an O-linked substituentselected from the group consisting of —OCH₂OCH₂R^(2B), —OCH₂R^(2B),—OC(O)R^(2B), —CH₂OC(O)R^(2A), —OC(O)N(R^(2A))(R^(2C)), and—OCH₂C(O)N(R^(2B))(R^(2C)), wherein R^(2B) and R^(2C) are independentlyselected from the group consisting of H, C₁-C₆ alkyl and C₂-C₆ alkenyl;and each R^(7B), when present, independently is —OH or —OCH₃.

42. The Ligand Drug Conjugate composition of embodiment 38 wherein thecomposition is represented by the structure(s) of:

wherein R^(2A) is hydrogen, an optionally substituted alkyl, saturatedor unsaturated, or R² along with the oxygen atom to which it is attacheddefines an O-linked substituent other than —OH; R³ is optionallysubstituted C₁-C₆ alkyl; R⁴ is methyl; R⁵ and R⁶ are side chain residuesof natural or un-natural hydrophobic amino acids, preferably of naturalhydrophobic amino acids, independently selected; and the—N(R^(7′))(R^(7′)) moiety is —NH(C₁-C₆ alkyl), optionally substituted by—CO₂H, or an ester thereof, or by an optionally substituted phenyl, oris —NH—N(C₁-C₆ alkyl)₂, wherein one and only one C₁-C₆ alkyl isoptionally substituted by —CO₂H, or an ester thereof, or by anoptionally substituted phenyl.

43. The Ligand Drug Conjugate composition of embodiment 42 wherein the—N(R^(7′))(R^(7′)) moiety is selected from the group consisting of—NH(CH₃), —NHCH₂CH₂Ph, and —NHCH₂—CO₂H, —NHCH₂CH₂CO₂H and—NHCH₂CH₂CH₂CO₂H.

44. The Ligand Drug Conjugate composition of embodiment 1 wherein LigandDrug Conjugate compounds of the composition are independentlyrepresented by the structure of:

wherein the curved dashed lines indicate optional cyclizations; Ab is anantibody Ligand Unit; S is a sulfur atom of the antibody Ligand Unit;the Ab-S— moiety is bonded to the carbon α or β to the indicated M³carboxylic acid; R^(2A) is hydrogen or optionally substituted alkyl, orR^(2A) along with the oxygen atom to which it is attached defines anO-linked substituent other than —OH, or R^(2A) is absent when R⁶ isbonded to that oxygen atom to define a substituted or unsubstitutedoxygen-containing heterocycloalkyl as indicated by the dash curved line;the circled Ar represents a 5-membered nitrogen-heteroarylene, whereinthe indicated required substituents to that heteroarylene are in a1,3-relationship with each other with optional substitution at theremaining positions; R³ is hydrogen or optionally substituted alkyl; R⁴,R⁵ and R⁶ are optionally substituted alkyl, independently selected, orR⁶ is bonded to the oxygen atom of the —OR^(2A) moiety in which R^(2A)is absent, as indicated by the curved dashed line between R⁶ and thatoxygen atom, and R⁴ and R⁵ are as previously defined; R^(4a) is hydrogenor optionally substituted alkyl and R^(4B) is optionally substitutedalkyl, or both together with the nitrogen to which they are attacheddefine a substituted or unsubstituted nitrogen quaternizedheterocycloalkyl, as indicated by the curved dash line between R^(4A)and R^(4B); one R⁷ is hydrogen or optionally substituted alkyl and theother R⁷ is optionally substituted aralkyl or heteroaralkyl; andsubscript p′ is an integer ranging from 1 to 24, preferably 1 to 20, ormore preferably from 1 to 16.

45. The Ligand Drug Conjugate composition of embodiment 44 whereinLigand Drug Conjugate compounds of the composition are independentlyrepresented by the structure of:

wherein subscript m is 0 or 1, preferably 1; Z is an optionally alkyleneor an optionally substituted alkenylene; R^(2A) is hydrogen oroptionally substituted alkyl or R along with the oxygen atom to which itis attached defines an O-linked substituent other than —OH; R³ ishydrogen or optionally substituted alkyl; R⁴, R⁵ and R⁶ are optionallysubstituted alkyl, independently selected; and R^(7A) is optionallysubstituted aryl or optionally substituted heteroaryl.

46. The Ligand Drug Conjugate composition of embodiment 45 whereinLigand Drug Conjugate compounds of the composition are independentlyrepresented by the structure of:

wherein R³ is optionally substituted alkyl; R⁴ is methyl; R⁵ and R⁶ areside chain residues of natural or un-natural hydrophobic amino acids,preferably of natural hydrophobic amino acids, independently selected;subscript p′ is an integer ranging from 1 to 8; subscript u, indicatingthe number of R^(7B) substituents, is 0, 1, 2 or 3, wherein each R^(7B),when present, is an independently selected O-linked substituent; andR^(8A) is hydrogen or optionally substituted alkyl.

47. The Ligand Drug Conjugate composition of embodiment 46 whereinLigand Drug Conjugate compounds of the composition are independentlyrepresented by the structure of:

wherein subscript u is 0, 1 or 2; each R^(7B), when present, isindependently —OH or —OCH₃; and R^(2A) is C₁-C₆ alkyl, —CH₂OR^(2B),—CH₂R^(2B), —C(═O)R^(2B), —CH₂C(═O)R^(2B), —C(═O)NHR^(2B) or—CH₂C(═O)NHR^(2B), wherein R^(2B) is C₁-C₆alkyl or C₂-C₆ alkenyl.

48. The Ligand Drug Conjugate composition of embodiment 1 wherein LigandDrug Conjugate compounds of the composition are represented by thestructure of:

wherein Ab is an antibody Ligand Unit, S is a sulfur atom from theantibody Ligand Unit; the Ab-S— moiety is bonded to the carbon α or β tothe indicated M³ carboxylic acid; R^(2A) is hydrogen, an optionallysubstituted alkyl, saturated or unsaturated, or R² along with the oxygenatom to which it is attached defines an O-linked substituent other than—OH; R³ is optionally substituted C₁-C₆ alkyl; R⁴ is methyl; R⁵ and R⁶are side chain residues of natural or un-natural hydrophobic aminoacids, preferably of natural hydrophobic amino acids, independentlyselected; and the —N(R^(7′))(R^(7′)) moiety is —NH(C₁-C₆ alkyl),optionally substituted by —CO₂H, or an ester thereof, or by anoptionally substituted phenyl, or is —N(C₁-C₆ alkyl)₂, wherein one andonly one C₁-C₆ alkyl is optionally substituted by —CO₂H, or an esterthereof, or by an optionally substituted phenyl; and subscript p′ is aninteger ranging from 1 to 8.

49. The Ligand Drug Conjugate composition of any one of embodiments 38to 48 wherein R^(2A) is saturated C₁-C₄ alkyl, unsaturated C₂-C₄ alkyl,—C(═O)R^(2B), wherein R^(2B) is C₁-C₄ alkyl; and subscript p is a numberranging from 1 to 8 or subscript p′ is an integer ranging from 1 to 8.

50. The Ligand Drug Conjugate composition of embodiment 49 whereinR^(2A) is saturated C₁-C₄ alkyl or unsaturated C₃-C₄ alkyl, whereinsaturated C₁-C₄ alkyl is —CH₃, —CH₂CH₃, or —CH₂CH₂CH₃ and unsaturatedC₃-C₄ alkyl is —CH₂CH═CH₂ or —CH(CH₃)CH═CH₂.

51. The Ligand Drug Conjugate composition of any one of embodiments 38to 50 wherein L_(P) is an amino acid residue of lysine, arginine,asparagine, glutamine, ornithine, citrulline, cysteine, homocysteine,penicillamine, threonine, serine, glutamic acid, aspartic acid,tyrosine, histidine or tryptophan, wherein the amino acid is in the D-or L-configuration

52. The Ligand Drug Conjugate composition of embodiment 38 wherein thecomposition is represented by the structure(s) of:

wherein A_(O) is absent or is an amine-containing acid residue;subscript p is an number ranging from 1 to 8; subscript q is an integerranging from 1 to 4; subscript u is 0 or 1; subscript v is an integerranging from 1 to 4; R^(7B), when present, is —OH; X^(LP) is selectedfrom the group consisting of —O—, —NH, —S— and —C(═O)—; and R^(E) andR^(F) are independently selected from the group consisting of —H andC₁-C₄ alkyl.

53. The Ligand Drug Conjugate composition of any one of embodiments 42to 44 wherein Ligand Drug Conjugate compounds of the composition areindependently represented by the structure(s) of:

wherein A_(O) is absent or is an amine-containing acid residue;subscript p′ is an integer ranging from 1 to 8; subscript q is aninteger ranging from 1 to 4; subscript u is 0 or 1; subscript v is aninteger ranging from 1 to 4; R^(7B), when present, is —OH; X^(LP) isselected from the group consisting of —O—, —NH, —S— and —C(═O)—; andR^(E) and R^(F) are independently selected from the group consisting of—H, and —C₁-C₄ alkyl.

54. The Ligand Drug Conjugate composition of any one of embodiments 38to 48 wherein A is —CH₂(CH₂)₄(C═O)— or —CH₂(CH₂)₄(C═O)NHCH₂CH₂(C═O)—.

55. The Ligand Drug Conjugate composition of any one of embodiments 38to 49 and 52 to 54 wherein R^(2A) is —C(O)CH₃.

56. The Ligand Drug Conjugate composition of any one of embodiments 39to 54 wherein R^(2A) is ethyl.

57. The Ligand Drug Conjugate composition of any one of embodiments 38to 54 wherein R^(2A) is —CH₂CH═CH₂.

58. The Ligand Drug Conjugate composition of any one of embodiments 38to 57 wherein A_(O) is a β-amino acid residue.

59. The Ligand Drug Conjugate composition of any one of embodiments 1 to58 wherein PEG has the structure selected from the group consisting of:

wherein the wavy line indicates site of attachment to X^(LP) of theParallel Connector Unit (L_(P)); R^(PEG1) is an optional PEG AttachmentUnit; R^(PEG2) is a PEG Capping Unit; R^(PEG3) is an PEG Coupling Unit;subscript n ranges from 2 to 72; each subscript n′ is independentlyselected from 1 to 72; and subscript e ranges from 2 to 5.

60. The Ligand Drug Conjugate composition of embodiment 52 or 53 wherein—X^(LP)-PEG has the structure of:

61. The Ligand Drug Conjugate composition of embodiment 60 whereinsubscript n is 12 and R^(PEG2) is hydrogen or —CH₃.

62. The Ligand Drug Conjugate composition of embodiment 1 wherein LigandDrug Conjugate compounds of the composition are independentlyrepresented by the structure of:

wherein Ab is an antibody Ligand Unit; S is a sulfur atom of theantibody Ligand Unit; the Ab-S— moiety is bonded to the carbon α or β tothe indicated M³ carboxylic acid; subscript u is 0 or 1; R^(7B), whenpresent, is —OH; and R^(2A) along with the oxygen atom to which it isattached is —OC(O)CH₃, —CH₂CH₃ or —CH₂CH═CH₂.

63. The Ligand Drug Conjugate composition of embodiment 1 wherein LigandDrug Conjugate compounds of the composition are independentlyrepresented by the structure of:

64. A Drug Linker compound, wherein the compound has the structure ofFormula 1:

wherein L_(B)′ is a Ligand Covalent Binding Unit precursor; L_(P) is aParallel Connector Unit; PEG is a Polyethylene Glycol Unit; subscripts aand b independently are 0 or 1; subscript n is 1, 2, 3 or 4; A is afirst optional Stretcher Unit so that subscript a is 0 when A is absentor 1 when A is present and is optionally comprised of two, three or foursubunits; B is an Branching Unit or a second optional Stretcher Unit(A_(O)) so that subscript b is 0 when B is absent or 1 when B is presentand is optionally comprised of two, three or four other subunits,wherein subscript b is 1 and B is a Branching when subscript n is 2, 3or 4, or subscript b is 0, or subscript b is 1 so that B is A_(O), whensubscript and is 1; Su is a carbohydrate moiety; —O′— represents anoxygen atom of an O-glycosidic bond cleavable by a glycosidase; -J′-represents a heteroatom, optionally substituted when nitrogen,preferably —NH—, or a nitrogen atom substituted by an optionallysubstituted alkyl, or an optionally substituted (heteroaryl)arylalkyl,from a functional group of B, when B is present, or from L_(P), when Bis absent; V, Z¹, Z² and Z³ are ═N— or ═C(R²⁴)—, wherein R²⁴ is hydrogenor alkyl, alkenyl or alkynyl, optionally substituted, or halogen, —NO₂,—CN or other electron withdrawing group, an electron donating group,—O′-Su, or —C(R⁸)(R⁹)-D⁺, wherein at least at least two of V, Z¹, Z² andZ³ are ═C(R²⁴)—, provided, one any only one R²⁴ is —C(R⁸)(R⁹)-D⁺ so that—C(R⁸)(R⁹)-D⁺ is bonded to one of V, Z¹, Z², Z³ when that variable groupis ═C(R²⁴)— and one and only one other R²⁴ is so that —O′-Su is bondedto another one of V, Z¹, Z², Z³ when that variable group is ═C(R²⁴)—,and the —O′Su and —C(R⁸)(R⁹)-D⁺ substituents are ortho or para to eachother; R⁸ and R⁹ independently are hydrogen, alkyl, alkenyl or alkynyl,optionally substituted, or aryl or heteroaryl, optionally substituted;R′ is hydrogen or is halogen, —NO₂, —CN or other electron withdrawinggroup; D⁺ is a quaternized tubulysin Drug Unit; and wherein saidglycosidase cleavage results in release of tubulysin compound (D) from aLigand Drug Conjugate compound prepared from the Linker Drug compound.

65. The Drug-Linker compound of embodiment 65 wherein L_(B)′- has astructure selected from the group consisting of:

wherein R is hydrogen or C₁-C₆ optionally substituted alkyl; R″ ishydrogen or halogen or R and R′ are independently selected halogen; T is—Cl, —Br, —I, —O-mesyl or —O— tosyl or other sulfonate leaving group; Uis —F, —Cl, —Br, —I, —O—N-succinimide, —O-(4-nitrophenyl),—O-pentafluorophenyl, —O-tetrafluorophenyl or —O—C(═O)—OR⁵⁷; and X² isC₁-C₁₀ alkylene, C₃-C₈-carbocycle, —O—(C₁-C₆ alkyl), -arylene-, C₁-C₁₀alkylene-arylene, -arylene-C₁-C₁₀ alkylene, —C₁-C₁₀alkylene-(C₃-C₆-carbocycle)-, —(C₃-C₈ carbocycle)-C₁-C₁₀ alkylene-,C₃-C₈-heterocycle, —C₁-C₁₀ alkylene-(C₃-C₈ heterocyclo)-,—C₃-C₈-heterocyclo)-C₁-C₁₀ alkylene, —(CH₂CH₂O)_(u), or—CH₂CH₂O)_(u)—CH₂—, wherein subscript u is an integer ranging from 1 to10 and R³⁷ is C₁-C₆ alkyl or aryl.

66. The Drug-Linker compound of embodiment 64 or 65 wherein -D⁺ is aquaternized tubulysin compound preferably having the structure of:

wherein the circle represents an 5-membered nitrogen-heteroarylene andwherein the indicated required substituents to that heteroarylene are ina 1,3-relationship with each other with optional substitution at theremaining positions; subscript m is 0 or 1; R^(2A) is hydrogen oroptionally substituted alkyl or R^(2A) along with the oxygen atom towhich it is attached defines an O-linked substituent other than —OH; R³is hydrogen or optionally substituted alkyl; R⁴, R⁵ and R⁶ areoptionally substituted alkyl; one R⁷ is an optionally substituted alkyl,an optionally substituted arylalkyl, optionally substitutedheteroarylalkyl and the other R⁷ is hydrogen or an optionallysubstituted alkyl; and R^(8A) is hydrogen or optionally substitutedalkyl, wherein the wavy line indicates covalent bonding of D⁺ to theremainder of the Drug Linker compound structure and wherein optionallysubstituted alkyl are independently selected.

67. The Drug-Linker compound of embodiment 66 wherein the compound hasthe structure of one of Formula IIA-IIF:

68. The Drug-Linker compound of any one of embodiments 64 to 67 wherein—O′-Su has the structure of Formula III:

wherein the wavy line represents covalent bonding of O′ to the remainderof the Drug Linker compound; and R⁴⁵ is —CH₂OH or —CO₂H.

69. The Drug-Linker compound of embodiment 68 wherein the compound hasthe structure of Formula IV:

wherein J′ is —N(R³³)—, wherein R³³ is hydrogen or methyl; V and Z³independently are ═CH— or ═N—; R′ is hydrogen or an electron withdrawinggroup; R⁸ is hydrogen; R⁹ is hydrogen, optionally substituted C₁-C₆alkyl or optionally substituted phenyl; and R⁴⁵ is —CO₂H.

70. The Drug-Linker compound of embodiment 64 wherein a is 1; andL_(B)′-A- of Formula I has the structure of Formula V:

wherein the —[C(R^(b1))(R^(b1))]_(q)—[HE]- moiety is A or A₁, wherein A₁is a subunit of A; A₂₋₄ are optional subunits of A; R is hydrogen,chloro or C₁-C₄ alkyl; R″ is hydrogen is or chloro; R^(a1) is hydrogen,optionally substituted alkyl or a Basic Unit (BU), optionally protected;and R^(a2) is hydrogen or optionally substituted alkyl, or R^(a1) andR^(a2) together with the carbon atom to which they are attached definesa substituted or unsubstituted nitrogen-containing heterocycloalkyl; HEis an optional Hydrolysis Enhancer (HE) Unit; subscript q is an integerranging from 0 to 6; each R^(b1) independently is hydrogen, optionallysubstituted C₁-C₆ alkyl, optionally substituted aryl or optionallysubstituted heteroaryl, or two R^(b1) together with the carbon(s) towhich they are attached comprise or preferably define, a substituted orunsubstituted C₃-C₆ cycloalkyl or one R^(b1) and HE together with thecarbon to which they are attached define a substituted or unsubstituted5 or 6-membered cycloalkyl or a substituted or unsubstituted 5- or6-membered heterocycloalkyl and the other R^(b1) is hydrogen, optionallysubstituted C₁-C₆ alkyl, optionally substituted aryl or optionallysubstituted heteroaryl; BU, optionally protected, has the structure of—[C(R¹)(R¹)]—[C(R²)(R²)]_(r)—N(R²²)(R²³), or an acid addition saltthereof, wherein subscript r is 0, 1, 2 or 3; each R¹ independently ishydrogen or lower alkyl or two R¹ together with the carbon to which theyare attached comprise, or preferably define, a substituted orunsubstituted C₃-C₆ cycloalkyl, and each R² independently is hydrogen,optionally substituted C₁-C₆ alkyl, optionally substituted aryl oroptionally substituted heteroaryl, or two R² together with the carbon(s)to which they are attached and any intervening carbons define asubstituted or unsubstituted C₃-C₆ cycloalkyl, or one R¹ and one R²together with the carbons to which they are attached and any interveningcarbons define a substituted or unsubstituted 5- or 6-memberedcycloalkyl, and the remaining R¹ and R² are as defined; and R²² and R²³independently, hydrogen, optionally substituted C₁-C₆ alkyl, or anacid-labile protecting group, or together with the nitrogen to whichthey are attached define a substituted or unsubstituted 5- or 6-memberedheterocycloalkyl, one of R²², R²³ is hydrogen and the other is an acidlabile protecting group.

71. The Drug Linker compound of embodiment 70 wherein Formula V has thestructure of Formula VA:

wherein subscript q is an integer ranging from 0 to 4.

72. The Drug Linker compound of embodiment 70 wherein Formula V has thestructure of Formula VB:

wherein one of R²², R²³ is hydrogen and the other is an acid labilecarbamate protecting group; and subscript q is an integer ranging from 0to 4.

73. The Drug Linker compound of embodiment 71 or 72 wherein Formula VAor Formula VB has the structure of:

respectively.

74. The Drug Linker compound of embodiment 70 wherein the compound hasthe structure of Formula VI:

wherein the asterisk (*) designates chirality or absence thereof at theindicated carbon; A₂₋₄ are independently selected optional subunits ofA, wherein —[C(R^(b1))(R^(b1))]_(q)—[HE]- is A₁ when one or more suchsubunits are present: one of R and R″ is hydrogen and the other ishydrogen or chloro; R′ is hydrogen or an electron withdrawing group;R^(a1) is hydrogen or a basic unit (BU), optionally protected, havingthe structure of —CH₂—N(R²²)(R²³), or an acid addition salt thereof,wherein R²² and R²³ independently are hydrogen, methyl or ethyl or bothtogether with the nitrogen atom to which they are attached comprise asubstituted or unsubstituted 5- or 6-membered heterocycloalkyl, or oneof R²², R²³ is hydrogen and the other is an acid labile carbamateprotecting group; R^(a2) is hydrogen; subscript q is an integer rangingfrom 0 to 5 when HE is present or 1 to 5 when HE is absent; each R^(b1)independently is hydrogen or optionally substituted C₁-C₆ alkyl; HE isabsent or is —C(═O)—; R⁴⁵ is —CO₂H; J′ is —NH—; V and Z³ are ═CH₂—; R⁸is hydrogen; and R⁹ is hydrogen or methyl.

75. The Drug Linker compound of embodiment 74 wherein the indicatedstarred (*) carbon is predominantly in the same absolute configurationas the alpha carbon of an L-amino acid when that indicated carbon ischiral.

76. The Drug Linker compound of any one of embodiments 67 to 69 whereinA and A_(O), when present, independently has the structure of Formula 7or Formula 8, or any one of embodiments 68 to 73, wherein each of A₂₋₄,when present, independently has the structure of Formula 7 or Formula 8:

wherein the wavy line indicates covalent bonding of the Formula 7 orFormula 8 structure within the Drug Linker structure; wherein K and Lindependently are C, N, O or S, provided that when K or L is O or S, R⁴¹and R⁴² to K or R⁴³ and R⁴⁴ to L are absent, and when K or L are N, oneof R⁴¹, R⁴² to K or one of R⁴³, R⁴⁴ to L are absent, and provided thatno two adjacent L are independently selected as N, O, or S; whereinsubscript s is an integer ranging from 0 to 12, and subscript t is aninteger ranging from 1 to 12; wherein G is hydrogen, optionallysubstituted C₁-C₆ alkyl, —OH, —OR^(G), —CO₂H, CO₂R^(G), wherein R^(G) isC₁-C₆ alkyl, aryl or heteroaryl, optionally substituted, or R^(PR),wherein R^(PR) is a suitable protecting group, —NH₂, or—N(R^(G))(R^(PG)), wherein R^(G) independently selected is as previouslydefined or both R^(G) together with the nitrogen to which they areattached comprise, or preferably define, a substituted or unsubstituted5- or 6-membered heterocycloalkyl or both R^(PR) together form asuitable protecting group; wherein R³⁸ is hydrogen or optionallysubstituted C₁-C₆ alkyl; R³⁹—R⁴⁴ independently are hydrogen, optionallysubstituted C₁-C₆ alkyl, optionally substituted, or optionallysubstituted heteroaryl, or both R³⁹, R⁴⁰ together with the carbon towhich they are attached comprise, or preferably define, a substituted orunsubstituted C₃-C₆ cycloalkyl, or R⁴¹, R⁴² together with K to whichthey are attached when K is C, or R⁴³, R⁴⁴ together with L to which theyare attached when L is C, comprise, or preferably define a substitutedor unsubstituted C₃-C₆ cycloalkyl, or R⁴⁰ and R⁴¹, or R⁴⁰ and R⁴³, orR⁴¹ and R⁴³ to together with the carbon or heteroatom to which they areattached and atoms intervening between those carbon and/or heteroatomscomprise, or preferably define, a substituted or unsubstituted 5- or6-membered cycloalkyl or heterocycloalkyl, or wherein A₁ is analpha-amino, beta-amino or another amine-containing acid residue.

77. The Drug Linker compound of any one of embodiments 64 to 76 wherein-D⁺ is a quaternized tubulysin compound preferably having the structureof:

wherein the dashed curved lines indicate optional cyclizations; R^(2A)is hydrogen or optionally substituted alkyl, or R^(2A) is hydrogen oroptionally substituted alkyl, or R^(2A) along with the oxygen atom towhich it is attached defines an O-linked substituent other than —OH, orR^(2A) is absent when R⁶ is bonded to that oxygen atom, as indicated bythe curved dash line between R⁶ and the oxygen atom, to define asubstituted or unsubstituted oxygen-containing heterocycloalkyl; thecircled Ar represents a 5-membered nitrogen-heteroaryl, wherein theindicated required substituents to that heteroaryl are in a1,3-relationship with each other with optional substitution at theremaining positions; R³ is hydrogen or optionally substituted alkyl; R⁴,R⁵ and R⁶ are is optionally substituted alkyl, independently selected,or R⁶ is bonded to the oxygen atom of the —OR^(2A) moiety in whichR^(2A) is absent and R⁴ and R⁵ are as previously defined; R^(4a) ishydrogen or optionally substituted alkyl and R^(4B) is optionallysubstituted alkyl, or both together with the nitrogen to which they areattached, as indicated by the curved dashed line between R^(4A) andR^(4B), define a substituted or unsubstituted quaternized nitrogenheterocycloalkyl; one R⁷ is hydrogen or optionally substituted alkyl andthe other R⁷ is optionally substituted aralkyl or heteroaralkyl; whereinthe wavy line indicates covalent bonding of the D⁺ structure to theremainder of the Drug Linker structure.

78. The Drug Linker compound of embodiment 77 wherein the quaternizedtubulysin Drug Unit (-D⁺) has the structure of:

subscript m is 0 or 1, preferably 1; Z is an optionally substitutedalkylene or an optionally substituted alkenylene; and R^(7A) isoptionally substituted aryl or optionally substituted heteroaryl.

79. The Drug Linker compound of embodiment 78 wherein the quaternizedtubulysin Drug Unit (-D⁺) has the structure of:

wherein R^(7A) is optionally substituted phenyl and R⁸ is hydrogen ormethyl.

80. The Drug Linker compound of embodiment 78 wherein the quaternizedtubulysin Drug Unit (-D⁺) has the structure of:

wherein R⁵ and R⁶ are alkyl side chain residues of natural hydrophobicamino acids, independently selected; subscript u, indicating the numberof R^(7B) substituents, is 0, 1, 2 or 3: each R^(7B), when present, isan independently selected O-linked substituent; and R^(8A) is hydrogenor optionally substituted alkyl.

81. The Drug Linker compound of embodiment 79 wherein the quaternizedtubulysin Drug Unit (-D⁺) has the structure of:

wherein R⁴ is methyl; subscript u is 0, 1 or 2; R³ is H, methyl, ethyl,propyl, —CH₂—OC(O)R^(3A), —CH₂CH(R^(3B))C(O)R^(A) or—CH(R^(3B))C(O)NHR^(3A), wherein R^(3A) is C₁-C₆ alkyl and R^(3B) is Hor C₁-C₆ alkyl, independently selected from R^(3A); R^(2A) along withthe oxygen atom to which it is attached is an O-linked substituentselected from the group consisting of —OCH₂OCH₂R^(2B), —OCH₂R^(2B),—OC(O)R^(2B), —CH₂OC(O)R^(2B), —OC(O)N(R^(2B))(R^(2C)), and—OCH₂C(O)N(R^(2B))(R^(2C)), wherein R^(2B) and R^(2C) are independentlyselected from the group consisting of H, C₁-C₆ alkyl and C₂-C₆ alkenyl;and each R^(7B), when present, independently is —OH or —OCH₃.

82. The Drug Linker compound of embodiment 77 wherein the quaternizedtubulysin Drug Unit (-D⁺) has the structure of:

wherein R^(2A) is hydrogen, an optionally substituted alkyl, saturatedor unsaturated, or R² along with the oxygen atom to which it is attacheddefines an O-linked substituent other than —OH; R³ is optionallysubstituted C₁-C₆ alkyl; R⁴ is methyl; R⁵ and R⁶ are alkyl side chainresidues of natural hydrophobic amino acids; and the —N(R^(7′))(R^(7′))moiety is —NH(C₁-C₆ alkyl), optionally substituted by —CO₂H, or an esterthereof, or by an optionally substituted phenyl, or is —N(C₁-C₆ alkyl)₂,wherein one and only one C₁-C₆ alkyl is optionally substituted by —CO₂H,or an ester thereof, or by an optionally substituted phenyl.

83. The Drug Linker compound of embodiment 82 wherein the—N(R^(7′))(R^(7′)) moiety is selected from the group consisting of—NH(CH₃), —NHCH₂CH₂Ph, and —NHCH₂—CO₂H, —NHCH₂CH₂CO₂H and—NHCH₂CH₂CH₂CO₂H.

84. The Drug Linker compound of any one of embodiments 78 to 83 whereinR^(2A) is —CH₂CH₃.

85. The Drug Linker compound of any one of embodiments 78 to 83 whereinR^(2A) is —CH₂—CH═CH₂ or —CH₂C(CH₃)═CH₂.

86. The Drug Linker compound of embodiment 81 wherein R^(2A) is —CH₂CH₃or —CH₂—CH═CH₂, or —CH₂C(CH₃)═CH₂. R^(2B) is —CH₃, R³ is —CH₃ andsubscript u is 0.

87. The Drug Linker compound of embodiment 81 wherein R^(2A) is —CH₂CH₃or —CH₂—CH═CH₂, R^(2B) is —CH₃, R³ is —CH, and subscript u is 1, whereinR^(7B) is —OH.

88. The Drug Linker compound of embodiment 81 wherein the quaternizedtubulysin Drug Unit (-D⁺) has the structure of:

wherein R^(2B) is —CH₃, —CH₂CH₃, —CH₂CH₂CH₃, —CH(CH₃)₂, —CH₂CH(CH₃)₂, or—CH₂C(CH₃)₃.

89. The Drug Linker compound of embodiment 81 wherein the quaternizedtubulysin Drug Unit (-D⁺) has the structure of:

wherein R^(2B) is hydrogen, methyl, or —OCH₃, or —OCH₂R_(2B) is—OCH₂CH═CH₂ or —OCH₂C(CH₃)═CH₂.

90. The Drug Linker compound of embodiment 81 wherein the quaternizedtubulysin Drug Unit (-D⁺) is that of tubulysin M, the structure of whichis:

91. The Drug Linker compound of any one of embodiments 70 to 90 whereinL^(P) is a aminoalkanedioic acid, a diaminoalkanoic acid, asulfur-substituted alkanedioic acid, a sulfur-substituted aminoalkanoicacid, a diaminoalkanol, an aminoalkanediol, a hydroxyl substitutedalkanedioic acid, a hydroxyl substituted aminoalkanoic acid or asulfur-substituted aminoalkanol residue, optionally substituted, whereinthe sulfur substituent is in reduced or oxidized form.

92. The Drug Linker compound of any one of embodiments 70 to 90 whereinL^(P) is an amino acid residue of lysine, arginine, asparagine,glutamine, ornithine, citrulline, cysteine, homocysteine, penicillamine,threonine, serine, glutamic acid, aspartic acid, tyrosine, histidine ortryptophan, wherein the amino acid is in the D- or L-configuration.

93. The Drug Linker compound of embodiment 91 wherein theaminoalkanedioic acid, diaminoalkanoic acid, sulfur-substitutedaminoalkanoic acid or hydroxyl substituted aminoalkanoic acid residuehas the structure of Formula A or Formula B:

wherein subscript v is an integer ranging from 1 to 4; subscript v′ isan integer ranging from 0 to 4; X^(LP) is selected from the groupconsisting of —O—, —NR^(LP)—, —S—, —S(═O)—, —S(═O)₂—, and —C(═O)—,—C(═O)N(R^(LP))—, —N(R^(LP))C(═O)N(R^(LP))—,—N(R^(LP))C(═NR^(LP))N(R^(LP))—, wherein each R^(LP) is independentlyselected from the group consisting of hydrogen and optionallysubstituted alkyl or two of R^(LP) together along with intervening atomsdefine a heterocycloalkyl with any remaining R^(LP) as previouslydefined; Ar is an arylene or heteroarylene, optionally substituted; eachR^(E) and R^(F) is independently selected from the group consisting of—H, optionally substituted alkyl, optionally substituted aryl andoptionally substituted heteroaryl, or R^(E) and R^(F) together with thesame carbon to which they are attached, or R^(E) and R^(F) from adjacentcarbons together with these carbons, define a substituted orunsubstituted cycloalkyl, with any remaining R^(E) and R^(F)substituents as previously defined; and wherein the wavy lines indicatescovalent attachment of the Formula A or Formula B structure within theDrug Linker compound structure.

94. The Drug Linker compound of embodiment 93 wherein -L^(P)(PEG)- hasthe structure of Formula A1 or A2:

wherein X^(LP) is selected from the group consisting of —O—, —NH, —S—and —C(═O)—; R^(E) and R^(F) are independently selected from the groupconsisting of —H and —C₁₋₄ alkyl; and wherein the wavy line indicatescovalent attachment of Formula A1 or Formula A2 within the Drug Linkercompound structure.

95. The Drug Linker compound of embodiment 70 wherein the compound hasthe structure of:

wherein the curved dashed lines indicate optional cyclizations; R^(2A)is hydrogen or optionally substituted alkyl, or R^(2A) is hydrogen oroptionally substituted alkyl, or R^(2A) along with the oxygen atom towhich it is attached defines an O-linked substituent other than —OH, orR^(2A) is absent when R⁶ is bonded to that oxygen atom, as indicated bythe curved dash line between R⁶ and the oxygen atom, to define asubstituted or unsubstituted oxygen-containing heterocycloalkyl; thecircled Ar represents a 5-membered nitrogen-heteroaryl, wherein theindicated required substituents to that heteroaryl are in a1,3-relationship with each other with optional substitution at theremaining positions; R³ is hydrogen or optionally substituted alkyl; R⁴,R⁵ and R⁶ are optionally substituted alkyl, independently selected, orR⁶ is bonded to the oxygen atom of the —OR^(2A) moiety in which R^(2A)is absent and R⁴ and R⁵ are as previously defined; R^(4a) is hydrogen oroptionally substituted alkyl and R^(4B) is optionally substituted alkyl,or both together with the nitrogen to which they are attached define asubstituted or unsubstituted nitrogen quaternized heterocycloalkyl, asindicated by the curved dashed line between R^(4A) and R^(4B); and oneR⁷ is hydrogen or optionally substituted alkyl and the other R⁷ isoptionally substituted aralkyl or heteroaralkyl.

96. The Drug Linker compound of embodiment 95 wherein the compound hasthe structure of:

subscript in is 0 or 1, preferably 0; Z is an optionally alkylene or anoptionally substituted alkenylene; and R^(7A) is optionally substitutedaryl or optionally substituted heteroaryl.

97. The Drug Linker compound of embodiment 96 wherein the compound hasthe structure of:

R³ is optionally substituted alkyl; R⁴ is methyl; R⁵ and R⁶ are alkylside chain residues of natural or un-natural hydrophobic amino acids,preferably of natural hydrophobic amino acids, independently selected;subscript u, indicating the number of R^(7B) substituents, is 0, 1, 2 or3; wherein each R^(7B), when present, is an independently selectedO-linked substituent; and R^(8A) is hydrogen or optionally substitutedalkyl.

98. The Drug Linker compound of embodiment 97 wherein compound has thestructure of:

wherein R⁴ is methyl; subscript u is 0, 1 or 2; R³ is H, methyl, ethyl,propyl, —CH₂—OC(O)R^(3A), —CH₂CH(R^(3B))C(O)R^(3A) or—CH(R^(3B))C(O)NHR^(3A), wherein R^(3A) is C₁-C₆ alkyl and R^(3B) is Hor C₁-C₆ alkyl, independently selected from R^(3A); R^(2A) along withthe oxygen atom to which it is attached is an O-linked substituentselected from the group consisting of —OCH₂OCH₂R^(2B), —OCH₂R^(2B),—OC(O)R^(2B), —CH₂OC(O)R^(2B), —OC(O)N(R^(2B))(R^(2C)), and—OCH₂C(O)N(R^(2B))(R^(2C)), wherein R^(2B) and R^(2C) are independentlyselected from the group consisting of H, C₁-C₆ alkyl and C₂-C₆ alkenyl;and each R^(7B), when present, independently is —OH or —OCH₃.

99. The Drug Linker compound of embodiment 70 wherein the compound hasthe structure of:

R^(2A) is hydrogen, an optionally substituted alkyl, saturated orunsaturated, or R² along with the oxygen atom to which it is attacheddefines an O-linked substituent other than —OH; R³ is optionallysubstituted C₁-C₆ alkyl; R⁴ is methyl; R⁵ and R⁶ are side chain residuesof natural or un-natural hydrophobic amino acids, preferably of naturalhydrophobic amino acids, independently selected; and the—N(R^(7′))(R^(7′)) moiety is —NH(C₁-C₆ alkyl), optionally substituted by—CO₂H, or an ester thereof, or by an optionally substituted phenyl, oris —NH(C₁-C₆ alkyl)₂, wherein one and only one C₁-C₆ alkyl is optionallysubstituted by —CO₂H, or an ester thereof, or by an optionallysubstituted phenyl.

100. The Drug Linker compound of embodiment 99 wherein the—N(R^(7′))(R^(7′)) moiety is selected from the group consisting of—NH(CH₃), —NHCH₂CH₂Ph, and —NHCH₂—CO₂H, —NHCH₂CH₂CO₂H and—NHCH₂CH₂CH₂CO₂H.

101. The Drug Linker compound of any one of embodiments 98 to 101wherein R^(2A) is C₁-C₄, saturated alkyl, C₂-C₄ unsaturated alkyl,—C(═O)R^(2B), wherein R^(2B) is C₁-C₄ alkyl.

102. The Drug Linker compound of embodiment 100 wherein R^(2A) issaturated C₁-C₄ alkyl or unsaturated C₃-C₄ alkyl, wherein saturatedC₁-C₄ alkyl is —CH₃, —CH₂CH₃, or —CH₂CH₂CH₃ and unsaturated C₃-C₄ alkylis —CH₂CH═CH₂ or —CH(CH₃)CH═CH₂.

103. The Drug Linker compound of any one of embodiments 95 to 102wherein L_(P) is an amino acid residue of lysine, arginine, asparagine,glutamine, ornithine, citrulline, cysteine, homocysteine, penicillamine,threonine, serine, glutamic acid, aspartic acid, tyrosine, histidine ortryptophan, wherein the amino acid is in the D- or L-configuration.

104. The Drug Linker compound of embodiment 64 wherein the compound hasthe structure of:

wherein A_(O) is absent or is an amine-containing acid residue;subscript q is an integer ranging from 1 to 4; subscript u is 0 or 1;subscript v is an integer ranging from 1 to 4; R^(7B), when present, is—OH; X^(LP) is selected from the group consisting of —O—, —NH, —S— and—C(═O)—; R^(E) and R^(F) are independently selected from the groupconsisting of —H, and C₁-C₄ alkyl; and one of R²², R²³ is hydrogen andthe other is an acid labile protecting group or R²² and R²³ are eachhydrogen with the nitrogen to which they are attached optionallyprotonated as an acid addition salt.

105. The Drug Linker compound of any one of embodiments 70 to 103wherein A is —CH₂(CH₂)₄(C═O)— or —CH₂(CH₂)₄(C═O)NHCH₂CH₂(C═O)—.

106. The Drug Linker compound of any one of embodiments 95 to 104wherein R^(2A) is —C(═O)CH₃.

107. The Drug Linker compound of any one of embodiments 95 to 104wherein R^(2A) is ethyl.

108. The Drug Linker compound of any one of embodiments 95 to 104wherein R^(2A) is —CH₂CH═CH₂.

109. The Drug Linker compound of any one of embodiments 95 to 104wherein A_(O) is a β-amino acid residue.

110. The Drug Linker compound of any one of embodiments 96 to 109wherein PEG has the structure selected from the group consisting of:

wherein the wavy line indicates site of attachment to X^(LP) of theParallel Connector Unit (L_(P)); R^(PEG1) is an optional PEG AttachmentUnit; R^(PEG2) is a PEG Capping Unit; R^(PEG3) is an PEG Coupling Unit;subscript n ranges from 2 to 72; each subscript n′ is independentlyselected from 1 to 72; and subscript e ranges from 2 to 5.

111. The Drug Linker compound of embodiment 104 wherein —X^(LP)-PEG hasthe structure of:

112. The Drug Linker compound of embodiment 111 wherein subscript n is12 and R^(PEG2) is hydrogen or —CH₃.

113. The Drug Linker compound of embodiment 104 wherein the compound hasthe structure of:

wherein subscript u is 0 or 1; R^(7B), when present, is —OH; R^(2A)along with the oxygen atom to which it is attached is —OC(═O)CH₃. CH₂CH₃or —CH₂CH═CH₂; and one of R²², R²³ is hydrogen and the other is an acidlabile carbamate protecting group or R²² and R²³ are each hydrogen withthe nitrogen to which they are attached optionally protonated as an acidaddition salt.

114. The Drug Linker compound of embodiment 113 wherein the compound hasthe structure of:

wherein subscript n is 0, 1 or 2.

115. A tubulysin compound having the structure of:

wherein the curved dashed line indicates optional cyclization; R^(2A) isunsaturated alkyl, optionally substituted; the circled Ar represents a5-membered nitrogen-containing heteroarylene, wherein the indicatedrequired substituents to that heteroarylene are in a 1,3-relationshipwith each other with optional substitution at the remaining positions;R³ is hydrogen or optionally substituted alkyl; R⁴, R⁵ and R⁶ areoptionally substituted alkyl, independently selected; R^(4a) is hydrogenor optionally substituted alkyl and R^(4B) is optionally substitutedalkyl, or both together with the nitrogen to which they are attached, asindicated by the curved dashed line, define a substituted orunsubstituted quaternized nitrogen heterocycloalkyl; and one R⁷ ishydrogen or optionally substituted alkyl and the other R⁷ is optionallysubstituted aralkyl or heteroaralkyl.

116. The tubulysin compound of embodiment 115 wherein the compound hasthe structure of:

subscript m is 0 or 1; R^(2A) is unsaturated C₃-C₆ alkyl; Z is anoptionally substituted alkylene or an optionally substituted alkenylene;and R^(7A) is optionally substituted aryl or optionally substitutedheteroaryl.

117. The tubulysin compound of embodiment 116 wherein the compound hasthe structure of:

wherein R^(7A) is optionally substituted phenyl and R⁸ is hydrogen ormethyl.

118. The tubulysin compound of embodiment 116 wherein the compound hasthe structure of:

wherein R^(2A) is unsaturated C₃-C₆ alkyl; R⁵ and R⁶ are alkyl sidechain residues of natural or un-natural hydrophobic amino acids,preferably of natural hydrophobic amino acids, independently selected;subscript u, indicating the number of R^(7B) substituents, is 0, 1, 2 or3; each R^(7B), when present, is an independently selected O-linkedsubstituent; and R^(8A) is hydrogen or optionally substituted alkyl.

119. The tubulysin compound of embodiment 117 wherein the compound hasthe structure of:

wherein R⁴ is methyl; subscript u is 0, 1 or 2; R³ is H, methyl, ethyl,propyl, —CH₂—OC(O)R^(3A), —CH₂CH(R^(3B))C(O)R^(3A) or—CH(R^(3B))C(O)NHR^(3A), wherein R^(3A) is C₁-C₆ alkyl and R^(3B) is Hor C₁-C₆ alkyl, independently selected from R^(3A); and each R^(7B),when present, independently is —OH or —OCH₃.

120. The tubulysin compound of embodiment 115 wherein the compound hasthe structure of:

wherein R^(2A) is unsaturated alkyl, optionally substituted; R³ isoptionally substituted C₁-C₆ alkyl; R⁴ is methyl; R⁵ and R⁶ are alkylside chain residues of natural or un-natural hydrophobic amino acids,preferably of natural amino acids; and the —N(R^(7′))(R^(7′)) moiety is—NH(C₁-C₆ alkyl), optionally substituted by —CO₂H, or an ester thereof,or by an optionally substituted phenyl, or is —N(C₁-C₆ alkyl)₂, whereinone and only one C₁-C₆ alkyl is optionally substituted by —CO₂H, or anester thereof, or by an optionally substituted phenyl.

121. The tubulysin compound of embodiment 119 wherein the—N(R^(7′))(R^(7′)) moiety is selected from the group consisting of—NH(CH₃), —NHCH₂CH₂Ph, and —NHCH₂—CO₂H, —NHCH₂CH₂CO₂H and—NHCH₂CH₂CH₂CO₂H.

122. The tubulysin compound of any one of embodiments 115 to 121 whereinR^(2A) is —CH₂—CH═CH₂.

123. The tubulysin compound of embodiment 115, wherein the compound hasthe structure of:

124. A tubulysin compound having the structure of:

wherein R^(2B) is —CH₂CH₃, —CH₂CH₂CH₃, —CH(CH₃)₂, —CH₂CH(CH₃)₂ or—CH₂C(CH₃)₃.

125. A method of preparing a Drug Linker compound comprising the step ofquaternizing a tubulysin compound of any one of embodiments 115 to 124with a Linker Unit precursor.

126. A Ligand Drug Conjugate composition, wherein the composition isrepresented by the structure of:

wherein L is a Ligand Unit; L_(B) is a Ligand Covalent Binding Unit;L_(P) is a Parallel Connector Unit; PEG is a Polyethylene Glycol Unit;subscripts a and b independently are 0 or 1; subscript n is 1, 2, 3 or4; A is a first optional Stretcher Unit so that subscript a is 0 when Ais absent or 1 when A is present and is optionally comprised of two,three or four independently selected subunits (A₁, A₂, A₃, A₄); B is anBranching Unit or a second optional Stretcher Unit (A_(O)) so thatsubscript b is 0 when B is absent or subscript b is 1 when B is presentand is optionally comprised of two, three or four subunits independentlyof A, wherein subscript b is 1 and B is a Branching when subscript n is2, 3 or 4, or subscript b is 0, or subscript b is 1 so that B is A_(O),when subscript n is 1; V, Z¹, Z² and Z³ are ═N— or ═C(R²⁴)—, wherein R²⁴is hydrogen or alkyl, alkenyl or alkynyl, optionally substituted, orhalogen, —NO₂, —CN or other electron withdrawing group, or —OCH₃ orother an electron donating group, or —C(R⁸)(R⁹)-D⁺, wherein at least oneof V, Z¹, and Z³ is ═C(R²⁴)—, provided that one any only one R²⁴ is—C(R⁸)(R⁹)-D⁺ so that —C(R⁸)(R⁹)-D⁺ is bonded to one of V, Z¹, and Z³when that variable group is ═C(R²⁴)—; R′ is hydrogen or —OCH₃ or otherelectron donating group; D⁺ is a quaternized tubulysin compound; J is aheteroatom, optionally substituted when nitrogen, preferably —NH—, or anitrogen atom substituted by an optionally substituted alkyl, or anoptionally substituted (heteroaryl)arylalkyl; W is a peptide comprisedof an amino acid sequence covalently attached to J through an amide bondwherein that amide bond is cleavable by a protease, wherein saidprotease cleavage initiates release of a tubulysin compound (D) from aLigand Drug Conjugate compound of the composition; and subscript p is anumber ranging from 1 to 24.

127. The Ligand Drug Conjugate composition of embodiment 126, whereinthe composition is represented by the structure of:

wherein W consists or is comprised of a dipeptide, wherein the dipeptideis at the distal end of W and the indicated bond is an amide bondspecifically or preferentially cleavable by an intracellular protease incomparison to freely circulating serum proteases.

128. The Ligand Drug Conjugate composition of embodiment 127, whereinthe dipeptide has the structure of;

wherein R³⁴ is benzyl, methyl, isopropyl, isobutyl, sec-butyl,—CH(OH)CH₃ or has the structure of

and R³⁵ is methyl, —(CH₂)₄—NH₂, —(CH₂)₃NH(C═O)NH₂, (CH₂)₃NH(C═NH)NH₂, or—(CH₂)₂CO₂H, wherein the wavy line at the dipeptide N-terminus indicatescovalent binding to A_(O) or to L_(P), depending on the presence orabsence of A_(O), respectively, and the wavy line at the dipeptideC-terminus indicates covalent binding to J.

129. The Ligand Drug Conjugate composition of embodiment 126, 127 or 128is wherein D⁺ is a tubulysin compound preferably having the structureof:

wherein the curved dashed lines indicate optional cyclizations; R^(2A)is hydrogen or optionally substituted alkyl, or R^(2A) along with theoxygen atom to which it is attached defines an O-linked substituentother than —OH, or R^(2A) is absent when R⁶ is bonded to that oxygenatom, as indicated by the curved dash line between R⁶ and the oxygenatom, to define a substituted or unsubstituted oxygen-containingheterocycloalkyl; the circled Ar represents a 5-memberednitrogen-heteroaryl, wherein the indicated required substituents to thatheteroaryl are in a 1,3-relationship with each other with optionalsubstitution at the remaining positions; R³ is hydrogen or optionallysubstituted alkyl; R⁴, R⁵ and R⁶ are optionally substituted alkyl,independently selected, or R⁶ is bonded to the oxygen atom of the—OR^(2A) moiety in which R^(2A) is absent and R⁴ and R⁵ are aspreviously defined; R^(4a) is hydrogen or optionally substituted alkyland R^(4B) is optionally substituted alkyl, or both together with thenitrogen to which they are attached, as indicated by the curved dottedline between R^(4A) and R^(4B), define a substituted or unsubstitutedquaternized nitrogen heterocycloalkyl; one R⁷ is hydrogen or optionallysubstituted alkyl and the other R² is optionally substituted aralkyl orheteroaralkyl; wherein the wavy line indicates covalent bonding of theD⁺ structure to the remainder of the Ligand Drug Conjugate structure.

130. The Ligand Drug Conjugate composition of embodiment 129 wherein thequaternized tubulysin Drug Unit (-D⁺) has the structure of:

subscript m is 0 or 1, preferably 0; Z is an optionally substitutedalkylene or an optionally substituted alkenylene; and R^(7A) isoptionally substituted aryl or optionally substituted heteroaryl.

131. The Ligand Drug Conjugate composition of embodiment 130 wherein thequaternized tubulysin Drug Unit (-D⁺) has the structure of:

wherein R^(7A) is optionally substituted phenyl and R⁸ is hydrogen ormethyl.

132. The Ligand Drug Conjugate composition of embodiment 130 wherein thequaternized tubulysin Drug Unit (-D⁺) has the structure of:

wherein R⁵ and R⁶ are alkyl side chain residues of natural or un-naturalhydrophobic amino acids, preferably of natural amino acids,independently selected; subscript u, indicating the number of R^(7B)substituents, is 0, 1, 2 or 3; each R^(7B), when present, is anindependently selected O-linked substituent; and R^(8A) is hydrogen oroptionally substituted alkyl.

133. The Ligand Drug Conjugate composition of embodiment 131 wherein thequaternized tubulysin Drug Unit (-D⁺) has the structure of:

wherein R⁴ is methyl; subscript u is 0, 1 or 2; R³ is H, methyl, ethyl,propyl, —CH₂—OC(O)R^(3A), —CH₂CH(R^(3B))C(O)R^(3A) or—CH(R^(3B))C(O)NHR^(3A), wherein R^(3A) is C₁-C₆ alkyl and R^(3B) is Hor C₁-C₆ alkyl, independently selected from R^(3A); R^(2A) along withthe oxygen atom to which it is attached is an O-linked substituentselected from the group consisting of —OCH₂OCH₂R^(2B), —OCH₂R^(2B),—OC(O)R^(2B), —CH₂OC(O)R^(2B), —OC(O)N(R^(2B))(R^(2C)), and—OCH₂C(O)N(R^(2B))(R^(2C)), wherein R^(2B) and R^(2C) are independentlyselected from the group consisting of H, C₁-C₆ alkyl and C₂-C₆ alkenyl;and each R^(7B), when present, independently is —OH or —OCH₃.

134. The Ligand Drug Conjugate composition of embodiment 133, whereinthe quaternized tubulysin Drug Unit (-D⁺) has the structure of:

wherein R^(2B) is —CH₃, —CH₂CH₃, —CH₂CH₂CH₃, —CH(CH₃)₂, —CH₂CH(CH₃)₂,—CH₂C(CH₃)₃.

135. The Ligand Drug Conjugate composition of embodiment 133, whereinthe quaternized tubulysin Drug Unit (-D⁺) has the structure of:

wherein R^(2B) is hydrogen, methyl or —OCH₃, or —OCH₂R^(2B) is—OCH₂CH═CH₂ or —OCH₂C(CH₃)═CH₂.

136. The Ligand Drug Conjugate composition of embodiment 126, whereinthe Ligand Drug Conjugate composition is represented by the structure(s)of

137. A Drug Linker compound, wherein the compound is represented by thestructure of:

wherein L_(B)′ is a Ligand Covalent Binding Unit precursor; L_(P) is aParallel Connector Unit; PEG is a Polyethylene Glycol Unit; subscripts aand b independently are 0 or 1; subscript n is 1, 2, 3 or 4; A is afirst optional Stretcher Unit so that subscript a is 0 when A is absentor 1 when A is present and is optionally comprised of two, three or fourindependently selected subunits (A₁, A₂, A₃, A₄); B is an Branching Unitor a second optional Stretcher Unit (A_(O)) so that subscript b is 0when B is absent or 1 when B is present and is optionally comprised oftwo, three or four subunits independently of A, wherein subscript b is 1and B is a Branching when subscript n is 2, 3 or 4 or subscript b is 0,or subscript h is 1 so that B is A_(O), when subscript n is 1; V, Z¹, Z²and Z³ are ═N— or ═C(R²⁴)—, wherein R²⁴ is hydrogen or alkyl, alkenyl oralkynyl, optionally substituted, or halogen, —NO₂, —CN or other electronwithdrawing group, or —OCH₃ or other an electron donating group, or—C(R⁸)(R⁹)-D⁺, wherein at least one of V, Z¹, and Z³ is ═C(R²⁴)—,provided that one any only one R²⁴ is —C(R⁸)(R⁹)-D⁺ so that—C(R⁸)(R⁹)-D⁺ is bonded to one of V, Z¹, and Z³ when that variable groupis ═C(R²⁴)—; R′ is hydrogen or —OCH₃ or other electron donating group;D⁺ is a quaternized tubulysin compound; J is a heteroatom, optionallysubstituted when nitrogen, preferably —NH—, or a nitrogen atomsubstituted by an optionally substituted alkyl, or an optionallysubstituted (heteroaryl)arylalkyl; W is a peptide comprised of an aminoacid sequence covalently attached to J through an amide bond whereinthat amide bond is cleavable by a protease, wherein said proteasecleavage initiates release of a tubulysin compound (D) from a LigandDrug Conjugate compound of the composition.

138. The Drug Linker compound of embodiment 137, wherein the compound isrepresented by the structure of:

wherein W consists or is comprised of a dipeptide, wherein the dipeptideis at the distal end of W and the indicated bond is an amide bondspecifically cleavable by an intracellular protease in comparison tofreely circulating serum proteases.

139. The Drug Linker compound of embodiment 138, wherein the dipeptidehas the structure of:

wherein R³⁴ is benzyl, methyl, isopropyl, isobutyl, sec-butyl,—CH(OH)CH₃ or has the structure of

and R³⁵ is methyl, —(CH₂)₄—NH₂, —(CH₂)₃NH(C═O)NH₂, (CH₂)₃NH(C═NH)NH₂, or—(CH₂)₂CO₂H, wherein the wavy line at the dipeptide N-terminus indicatescovalent binding to A_(O) or to L_(P), depending on the presence orabsence of A_(O), respectively, and the wavy line at the dipeptideC-terminus indicates covalent binding to J.

140. The Drug Linker compound of embodiment 137, 138 or 139 wherein D⁺is a tubulysin compound preferably having the structure of:

wherein the curved dashed lines indicate optional cyclizations; R^(2A)is hydrogen or optionally substituted alkyl, or R^(2A) along with theoxygen atom to which it is attached defines an O-linked substituentother than —OH, or R^(2A) is absent when R⁶ is bonded to that oxygenatom, as indicated by the curved dash line between R⁶ and the oxygenatom, to define a substituted or unsubstituted oxygen-containingheterocycloalkyl; the circled Ar represents a 5-memberednitrogen-heteroaryl, wherein the indicated required substituents to thatheteroaryl are in a 1,3-relationship with each other with optionalsubstitution at the remaining positions; R³ is hydrogen or optionallysubstituted alkyl; R⁴, R⁵ and R⁶ are optionally substituted alkyl,independently selected, or R⁶ is is bonded to the oxygen atom of the—OR^(2A) moiety in which R^(2A) is absent and R⁴ and R⁵ are aspreviously defined; R^(4a) is hydrogen or optionally substituted alkyland R^(4B) is optionally substituted alkyl, or both together with thenitrogen to which they are attached, as indicated by the curved dottedline between R^(4A) and R^(4B), define a substituted or unsubstitutedquaternized nitrogen heterocycloalkyl; one R⁷ is hydrogen or optionallysubstituted alkyl and the other R⁷ is optionally substituted aralkyl orheteroaralkyl; wherein the wavy line indicates covalent bonding of theD⁺ structure to the remainder of the Ligand Drug Conjugate structure.

141. The Drug Linker compound of embodiment 140 wherein the quaternizedtubulysin Drug Unit (-D⁺) has the structure of:

subscript m is 0 or 1, preferably 1; Z is an optionally substitutedalkylene or an optionally substituted alkenylene; and R^(7A) isoptionally substituted aryl or optionally substituted heteroaryl.

142. The Drug Linker compound of embodiment 141 wherein the quaternizedtubulysin Drug Unit (-D⁺) has the structure of:

wherein R^(2A) is optionally substituted phenyl and R⁸ is hydrogen ormethyl.

143. Drug Linker compound of embodiment 141 wherein the quaternizedtubulysin Drug Unit -D⁺ has the structure of:

wherein R⁵ and R⁶ are alkyl side chain residues of natural or un-naturalhydrophobic amino acids, preferably of natural hydrophobic amino acids,independently selected; subscript u, indicating the number of R^(7B)substituents, is 0, 1, 2 or 3; each R^(7B), when present, is anindependently selected O-linked substituent; and R^(8A) is hydrogen oroptionally substituted alkyl.

144. Drug Linker compound of embodiment 142 wherein the quaternizedtubulysin Drug Unit (-D⁺) has the structure of:

wherein R⁴ is methyl; subscript u is 0, 1 or 2; R³ is H, methyl, ethyl,propyl, —CH₂—OC(O)R^(3A), —CH₂CH(R^(3B))(O)R^(3A) or—CH(R^(3B))C(O)NHR^(3A), wherein R^(3A) is C₁-C₆ alkyl and R^(3B) is Hor C₁-C₆ alkyl, independently selected from R^(3A); R^(2A) along withthe oxygen atom to which it is attached is an O-linked substituentselected from the group consisting of —OCH₂OCH₂R^(2B), —OCH₂R^(2B),—OC(O)R^(2B), —CH₂OC(O)R^(2B), —OC(O)N(R^(2B))(R^(2C)), and—OCH₂C(O)N(R^(2B))(R^(2C)), wherein R^(2B) and R^(2C) are independentlyselected from the group consisting of H, C₁-C₆ alkyl and C₂-C₆ alkenyl;and each R^(7B), when present, independently is —OH or —OCH₃.

145. Drug Linker compound of embodiment 144, wherein the quaternizedtubulysin Drug Unit (-D⁺) has the structure of:

wherein R^(2B) is —CH₃, —CH₂CH₃, —CH₂CH₂CH₃, —CH(CH₃)₂, —CH₂CH(CH₃)₂,—CH₂C(CH₃)₃.

146. Drug Linker compound of embodiment 144, wherein the quaternizedtubulysin Drug Unit (-D⁺) has the structure of:

wherein R^(2B) is hydrogen, methyl or —OCH₃, or —OCH₂R^(2B) is—OCH₂CH═CH₂ or —OCH₂C(CH₃)═CH₂.

147. The Drug Linker compound of embodiment 137, wherein the compoundhas the structure of:

wherein one of R²², R²³ is hydrogen and the other is an acid labileprotecting group or R²² and R²³ are each hydrogen with the nitrogen towhich they are attached optionally protonated as an acid addition salt.

148. A formulation comprising a Ligand Drug Conjugate of any one ofembodiments 1 to 63 and 126 to 136 and one or more excipients.

149. The formulation of embodiment 148 wherein the formulation is apharmaceutically acceptable formulation or a precursor thereof.

150. The formulation of embodiment 149 wherein the pharmaceuticallyacceptable formulation precursor is a solid suitable for reconstitutionas a solution for intravenous injection to a subject.

151. The formulation of embodiment 149 wherein the pharmaceuticallyacceptable formulation is a liquid suitable for intravenous injection toa subject.

152. The formulation of embodiments 149, 150 or 151 wherein the LigandDrug Conjugate is present in the pharmaceutically acceptable formulationor precursor thereof in an effective amount for treatment of ahyperproliferative condition.

153. A method of treating a hyperproliferative disease or conditioncomprising the step of administering to a patient having said disease orcondition an effective amount of a Ligand Drug Conjugate of any one ofembodiments 1 to 63 and 126 to 136.

154. The method of embodiment 153 wherein the hyperproliferative diseaseor condition is a cancer.

155. The method of embodiment 154 wherein the hyperproliferative diseaseor condition is a leukemia or a lymphoma.

156. A method of inhibiting the multiplication of a tumor cell or cancercell, or causing apoptosis in a tumor or cancer cell, by exposing saidcell with an effective amount of Ligand Drug Conjugate of any one ofembodiments 1 to 63 and 126 to 136 or of a tubulysin compound of any oneof embodiments 115 to 124.

1A. An Antibody Drug Conjugate having the structure of:

or one of Formula 2A-2F:

preferably in pharmaceutically acceptable salt form, wherein Ab is anantibody Ligand Unit, wherein a targeted moiety of the antibody LigandUnit is an accessible cell-surface antigen of targeted abnormal cells,wherein that antigen is preferentially present on the targeted abnormalcells in comparison to normal cells, or the targeted moiety of theantibody Ligand Unit is an accessible cell-surface antigen of a vascularepithelial cell in the vicinity of abnormal cells, wherein that antigenis preferably more abundant on the epithelial cell in comparison toepithelial cells in the periphery; and wherein either cell-surfaceantigen is capable of cellular internalization of bound ADC; L_(B) is aLigand Covalent Binding Unit; Le is a Parallel Connector Unit; PEG is aPolyethylene Glycol Unit; subscripts a and b independently are 0 or 1;subscript n is 1, 2, 3 or 4; A is a first optional Stretcher Unit sothat subscript a is 0 when A is absent or 1 when A is present and isoptionally comprised of two, three or four independently selectedsubunits (A₁, A₂, A₃, A₄); B is an Branching Unit or a second optionalStretcher Unit (A_(O)) so that subscript b is 0 when B is absent orsubscript b is 1 when B is present and is optionally comprised of two,three or four subunits independently of A, wherein subscript b is 1 andB is a Branching when subscript n is 2, 3 or 4, or subscript b is 0, orsubscript b is 1 so that B is A_(O), when subscript n is 1; Su is acarbohydrate moiety; —O′— represents an oxygen atom of an O-glycosidicbond cleavable by a glycosidase; -J′- represents a heteroatom,optionally substituted when nitrogen, from a functional group of B orA_(O), when either are present, or from L_(P), when either are absent;V, Z¹, Z² and Z³ are ═N— or ═C(R²⁴)—, wherein R²⁴ is hydrogen or alkyl,alkenyl or alkynyl, optionally substituted, or halogen, —NO₂, —CN orother electron withdrawing group, an electron donating group, —O′-Su, or—C(R⁸)(R⁹)-D⁺, wherein at least at least two of V, Z¹, Z² and Z³ are═C(R²⁴)—, provided, one any only one R²⁴ is —C(R⁸)(R⁹)-D⁺ so that—C(R⁸)(R⁹)-D⁺ is bonded to one of V, Z¹, Z², Z³ when that variable groupis ═C(R²⁴)— and one and only one other R²⁴ is so that —O′-Su is bondedto another one of V, Z¹, Z², Z³ when that variable group is ═C(R²⁴)—,and the —O′-Su and —C(R⁸)(R⁹)-D⁺ substituents are ortho or para to eachother, R⁸ and R⁹ independently are hydrogen, alkyl, alkenyl or alkynyl,optionally substituted, or aryl or heteroaryl, optionally substituted;R′ is hydrogen or is halogen, —NO₂, —CN or other electron withdrawinggroup;

D⁺ is a quaternized tubulysin Drug Unit preferably having the structureof:

wherein the circle represents an 5-membered nitrogen-heteroarylene andwherein the indicated required substituents to that heteroarylene are ina 1,3-relationship with each other with optional substitution at theremaining positions; subscript m is 0 or 1; R^(2A) is hydrogen oroptionally substituted alkyl, or R^(2A) along with the oxygen atom towhich it is attached defines an O-linked substituent; R³ is hydrogen oroptionally substituted alkyl; R⁴, R⁵ and R⁶ are optionally substitutedalkyl; one R⁷ is an optionally substituted alkyl, an optionallysubstituted arylalkyl, optionally substituted heteroarylalkyl and theother R⁷ is hydrogen or an optionally substituted alkyl; and R^(8A) ishydrogen or optionally substituted alkyl, wherein the wavy lineindicates covalent bonding of the quaternized tubulysin Drug Unit to theremainder of the Formula 2A-2F structures and wherein each optionallysubstituted alkyl is independently selected; and subscript p is anaverage drug loading having a number ranging from 1 to 24.

2A. The Antibody Drug Conjugate of embodiment 1A wherein —O′-Su has thestructure of Formula 3:

wherein the wavy line represents covalent bonding of O′ to the remainderof the LDC structure; and R⁴⁵ is —CH₂OH or —CO₂H.

3A. The Antibody Drug Conjugate of embodiment 2A having the structure ofFormula 4:

J′ is —N(R³³)—, wherein R³³ is hydrogen or methyl; V and Z³independently are ═CH— or ═N—; R′ is hydrogen or an electron withdrawinggroup; R⁸ is hydrogen; R⁹ is hydrogen, optionally substituted C₁-C₆alkyl or optionally substituted phenyl; and R⁴⁵ is —CO₂H.

4A. The Antibody Drug Conjugate of embodiment 1A wherein a is 1; and-L_(B)-A- has the structure of Formula 5:

wherein the —[C(R^(b1))(R^(b1))]_(q)—[HE]- moiety is A or A₁, wherein A₁is a subunit of A; A₂₋₄ are optional subunits of A; R is hydrogen orC₁-C₄ alkyl; R^(a1) is hydrogen, optionally substituted alkyl or a BasicUnit (BU); and R^(a2) is hydrogen or optionally substituted alkyl, orR^(a1) and R^(a2) together with the carbon atom to which they areattached define a nitrogen-containing heterocycloalkyl; HE is anoptional Hydrolysis Enhancer (HE) Unit; subscript q is an integerranging from 0 to 6; each R independently is hydrogen, optionallysubstituted C₁-C₆ alkyl, optionally substituted aryl or optionallysubstituted heteroaryl, or two R^(b1) together with the carbon(s) towhich they are attached comprise, or preferentially define, a C₃-C₆cycloalkyl or one R^(b1) and HE together with the carbon to which theyare attached define a 5 or 6-membered cycloalkyl or a 5- or 6-memberedheterocycloalkyl and the other R^(b1) is hydrogen, optionallysubstituted C₁-C₆ alkyl, optionally substituted aryl or optionallysubstituted heteroaryl; BU has the structure of—[C(R¹)(R¹)]—[C(R²)(R²)]_(r)—N(R²²)(R²³), or an acid addition saltthereof, wherein subscript r is 0, 1, 2 or 3; each R¹ independently ishydrogen or C₁-C₄ alkyl or two R¹ together with the carbon to which theyare attached comprise, or preferably define, a C₃-C₆ cycloalkyl, andeach R² independently is hydrogen, optionally substituted C₁-C₆ alkyl,optionally substituted aryl or optionally substituted heteroaryl, or twoR² together with the carbon(s) to which they are attached and anyintervening carbons define a C₃-C₆ cycloalkyl, or one R¹ and one R²together with the carbons to which they are attached and any interveningcarbons define a 5- or 6-membered cycloalkyl and the remaining R¹ and R²are as defined; R²² and R²³ independently are hydrogen or optionallysubstituted C₁-C₆ alkyl or together with the nitrogen to which they areattached define a 5- or 6-membered heterocycloalkyl, or one of R²², R²³is hydrogen and the other is an acid labile protecting group; andwherein the dotted line is an optional double bond and the wavy line tothe succinimide (double bond is absent) or maleimide ring (double bondis present) of L_(B) indicates covalent bonding of sulfur derived from asulfhydryl group of an antibody and the other wavy line indicatescovalent bonding to the remainder of the Antibody Drug Conjugatestructure.

5A. The Antibody Drug Conjugate of embodiment 4A wherein Formula 5 hasthe structure of Formula 5A:

wherein subscript q is an integer ranging from 0 to 4.

6A. The Antibody Drug Conjugate of embodiment 4A wherein Formula 5 hasthe structure of Formula 5B, or an acid addition salt thereof:

wherein R²² and R²³ are each hydrogen or one of R²², R²³ is hydrogen andthe other is an acid labile carbamate protecting group; and subscript qis an integer ranging from 0 to 4.

7A. The Antibody Drug Conjugate of embodiment 5A or 6A wherein Formula5A or Formula 5B has the structure of:

wherein X⁻ is chloride, acetate, trifluoroacetate or dihydrogenphosphate.

8A. The Antibody Drug Conjugate of embodiment 4A having the structure ofFormula 6:

wherein S is a sulfur atom of the antibody Ligand Unit; the asterisk (*)designates chirality or absence thereof at the indicated carbon; A₂₋₄are independently selected optional subunits of A, wherein—[C(R^(b1))(R^(b1))]_(q)—[HE]- is A₁ when one or more such subunits arepresent; R is hydrogen; R′ is hydrogen or an electron withdrawing group;R^(a1) is hydrogen or a basic unit (BU) wherein BU is a Basic Unithaving the structure of —CH₂—N(R²²)(R²³), or an acid addition saltthereof, wherein R²² and R²³ independently are hydrogen, methyl or ethylor both together with the nitrogen atom to which they are attachedcomprise, or preferably define, a 5- or 6-membered heterocycloalkyl, orone of R²², R²³ is hydrogen and the other is an acid labile carbamateprotecting group; R^(a2) is hydrogen; subscript q is an integer rangingfrom 0 to 5 when HE is present or 1 to 5 when HE is absent; each R^(b1)independently is hydrogen or optionally substituted C₁-C₆ alkyl; HE isabsent or is —C(═O)—; R⁴⁵ is —CO₂H; J′ is —NH—; V and Z³ are each ═CH₂—;R⁸ is hydrogen; R⁹ is hydrogen or methyl; and subscript p is a numberranging from 1 to 16.

9A. The Antibody Drug Conjugate of embodiment 1A represented by thestructure(s) of Formula 9A and/or Formula 9B:

wherein S is a sulfur atom of the antibody Ligand Unit; A₂₋₄ areindependently selected optional subunits of A, wherein—[C(R^(b1))(R^(b1))]_(q)-[HE]- is A when one or more, such subunits arepresent; R is hydrogen; R′ is hydrogen or an electron withdrawing group;R^(a1) is —H or BU wherein BU is a Basic Unit having the structure of—CH₂—N(R²²)(R²³), or an acid addition salt thereof, wherein R²² and R²³independently are hydrogen or methyl or both together with the nitrogenatom to which they are attached define a basic nitrogen-containing 5- or6-membered heterocycloalkyl, or one of R²², R²³ is hydrogen and theother is an acid labile protecting group; R^(a2) is hydrogen; subscriptq is an integer ranging from 0 to 5 when HE is present or from 1 to 5when HE is absent; each R^(b1) independently is hydrogen or optionallysubstituted C₁-C₆ alkyl; HE is absent or is —C(═O)—; J′ is —O— or —NH—;and R⁸ and R⁹ are independently —H or optionally substituted alkyl orboth together along with the carbon atom to which they are attacheddefine a cycloalkyl; and

10A. The Antibody Drug Conjugate of embodiment 9A represented by thestructure(s) of Formula 10A and/or Formula 10B:

wherein R is hydrogen; R′ is hydrogen, —NO₂, —Cl or —F; HE is —C(═O)—;R⁴⁵ is —CO₂H; J′ is —NH—; V and Z³ are each ═CH₂—; R⁸ is hydrogen; andR⁹ is hydrogen or methyl.

11A. The Antibody Drug Conjugate of embodiment 8A, 9A or 10A wherein theindicated starred (*) carbon is predominantly in the same absoluteconfiguration as the alpha carbon of an L-amino acid when that indicatedcarbon is chiral.

12A. The Antibody Drug Conjugate of any one of embodiments 1A to 10A,wherein A, A_(O), and each of A₂₋₄, when present, independently have thestructure of Formula 7 or Formula 8:

wherein the wavy lines indicated covalent attachment within theremainder of L_(O), wherein K and L independently are C, N, O or S,provided that when K or L is O or S, R⁴¹ and R⁴² to K or R⁴³ and R⁴⁴ toL are absent, and when K or L are N, one of R⁴¹, R⁴² to K or one of R⁴²,R⁴³ to L are absent, and provided that no two adjacent L areindependently selected as N, O, or S; wherein subscripts e and f areindependently selected integers that range from 0 to 12, and subscript gis an integer ranging from 1 to 12; G is hydrogen, optionallysubstituted C₁-C₆ alkyl, —OH, —OR^(PR), —CO₂H, CO₂RP, wherein R^(PR) isa suitable protecting, —N(R^(PR))(R^(PR)), wherein R^(PR) areindependently a protecting group or R^(PR) together form a suitableprotecting group, or —N(R⁴⁵)(R⁴⁶), wherein one of R⁴⁵, R⁴⁶ is hydrogenor R^(PR), wherein R^(PR) is a suitable protecting group, and the otheris hydrogen or optionally substituted C₁-C₆ alkyl; wherein R³⁸ ishydrogen or optionally substituted C₁-C₆ alkyl; R³⁹—R⁴⁴ independentlyare hydrogen, optionally substituted C₁-C₆ alkyl, optionally substitutedaryl, or optionally substituted heteroaryl, or both R³⁹, R⁴⁰ togetherwith the carbon to which they are attached comprise or preferably definea C₃-C₆ cycloalkyl, or R⁴¹, R⁴² together with K to which they areattached when K is C, or R⁴³, R⁴⁴ together with L to which they areattached when L is a carbon atom comprise a C₃-C₆ cycloalkyl, or R⁴⁰ andR⁴¹, or R⁴⁰ and R⁴³, or R⁴¹ and R⁴³ to together with the carbon atom orheteroatom to which they are attached and the atoms intervening betweenthose carbon atoms and/or heteroatoms comprise or preferably define a 5-or 6-membered cycloalkyl or heterocycloalkyl, provided that when K is Oor S, R⁴¹ and R⁴² are absent, when K is N, one of R⁴¹, R⁴² is absent,when L is O or S, R⁴¹ and R⁴² are absent, and when L is N, one of R⁴³,R⁴⁴ is absent, or wherein A_(O) has a structure corresponding to analpha-amino, beta-amino or another amine-containing acid.

13A. The Antibody Drug Conjugate of any one of embodiments 1A to 12Awherein the quaternized tubulysin Drug Unit (-D⁺) has the structure of:

R^(2A) is hydrogen or optionally substituted alkyl, or R^(2A) along withthe oxygen atom to which it is attached defines an O-linked substituentother than —OH, or R^(2A) is absent when R⁶ is bonded to that oxygenatom, as indicated by the curved dash line between R⁶ and the oxygenatom, to define an oxygen-containing heterocycloalkyl; the circled Arrepresents a 5-membered nitrogen-heteroarylene, wherein the indicatedrequired substituents to that heteroarylene are in a 1,3-relationshipwith each other with optional substitution at the remaining positions;R³ is hydrogen or optionally substituted alkyl; R⁴, R⁵ and R⁶ areoptionally substituted alkyl, independently selected, or R⁶ is bonded tothe oxygen atom of the —OR^(2A) moiety in which R^(2A) is absent and R⁴and R⁵ are as previously defined; R^(4a) is hydrogen or optionallysubstituted alkyl and R^(4B) is optionally substituted alkyl, or bothtogether with the nitrogen to which they are attached, as indicated bythe is curved dotted line between R^(4A) and R^(4B), define aquaternized nitrogen heterocycloalkyl, optionally substituted; one R⁷ ishydrogen or optionally substituted alkyl and the other R⁷ is optionallysubstituted aralkyl or heteroaralkyl; wherein the wavy line indicatescovalent bonding to the remainder of the Antibody Drug Conjugatestructure.

14A. The Antibody Drug Conjugate of embodiment 13A wherein thequaternized tubulysin Drug Unit (-D⁺) has the structure of:

subscript m is 0 or 1; Z is an optionally substituted alkylene or anoptionally substituted alkenylene; and R^(7A) is optionally substitutedaryl or optionally substituted heteroaryl.

15A. The Antibody Drug Conjugate of embodiment 14A wherein thequaternized tubulysin Drug Unit (-D⁺) has the structure of:

wherein R^(7A) is optionally substituted phenyl and R⁸ is hydrogen ormethyl.

16A. The Antibody Drug Conjugate of embodiment 14A wherein thequaternized tubulysin Drug Unit (-D⁺) has the structure of:

wherein R⁵ and R⁶ are alkyl side chain residues of natural hydrophobicamino acids, independently selected; subscript u, indicating the numberof R^(7B) substituents, is 0, 1, 2 or 3; each R^(7B), when present, isan independently selected O-linked substituent; and R^(8A) is hydrogenor optionally substituted alkyl.

17A. The Antibody Drug Conjugate of embodiment 15A wherein thequaternized tubulysin Drug Unit (-D⁺) has the structure of:

wherein R⁴ is methyl; subscript u is 0, 1 or 2; R³ is H, methyl, ethyl,propyl, —CH₂—(C(O)R^(3A), —CH₂CH(R^(3B))C(O)R^(3A) or—CH(R^(3B))C(O)NHR^(3A), wherein R^(3A) is C₁-C₅ is alkyl and R^(3B) isH or C t-C₆ alkyl, independently selected from R^(3A); R^(2A) along withthe oxygen atom to which it is attached is an O-linked substituentselected from the group consisting of —OCH₂OCH₂R^(2B), —OCH₂R^(2B),—OC(O)R^(2B), —CH₂OC(O)R^(2B), —OC(O)N(R^(2A))(R^(2C)), and—OCH₂C(O)N(R^(2B))(R^(2C)), wherein R^(2B) and R^(2C) are independentlyselected from the group consisting of H, C₁-C₆ alkyl and C₂-C₆ alkenyl;and each R^(7B), when present, independently is —OH or —OCH₃.

18A. The Antibody Drug Conjugate of embodiment 13A wherein thequaternized tubulysin Drug Unit (-D⁺) has the structure of:

wherein R^(2A) is hydrogen, an optionally substituted alkyl, saturatedor unsaturated, or R² along with the oxygen atom to which it is attacheddefines an O-linked substituent other than —OH; R³ is optionallysubstituted C₁-C₆ alkyl; R⁴ is methyl; R⁵ and R⁶ are alkyl side chainresidues of natural hydrophobic amino acids; and the —N(R^(7′))(R^(7′))moiety is —NH(C₁-C₆ alkyl), optionally substituted by —CO₂H, or an esterthereof, or by an optionally substituted phenyl, or is —NH—N(C₁-C₆alkyl)₂, wherein one and only one C₁-C₆ alkyl is optionally substitutedby —CO₂H, or an ester thereof, or by an optionally substituted phenyl.

19A. The Antibody Drug Conjugate of embodiment 18A wherein the—N(R^(7′))(R^(7′)) moiety is selected from the group consisting of—NH(CH₃), —NHCH₂CH₂Ph, and —NHCH₂—CO₂H, —NHCH₂CH₂CO₂H and—NHCH₂CH₂CH₂CO₂H.

20A. The Antibody Drug Conjugate of any one of embodiments 11A to 18A,wherein R^(2A) is —CH₂CH₃.

21 A. The Antibody Drug Conjugate of any one of embodiments 11A to 18Awherein R^(2A) is —CH₂—CH═CH₂.

22A. The Antibody Drug Conjugate of any one of embodiment 17A or 18Awherein R^(2A) is —CH₂CH₃, —CH₂—CH═CH, or —CH₂C(CH₃)═CH₂, R^(2B) is—CH₃, R³ is —CH₃ and subscript u is 0.

23A. The Antibody Drug Conjugate of embodiment 17A or 18A wherein R^(2A)is —CH₂CH₃ or —CH₂—CH═CH₂, or —CH₂C(CH₃)═CH₂, R^(2B) is —CH₃, R³ is —CH₃and subscript u is 1, wherein R^(7B) is —OH.

24A. The Antibody Drug Conjugate of any one of embodiments 1A to 23Awherein L_(P) is a aminoalkanedioic acid, a diaminoalkanoic acid, asulfur-substituted alkanedioic acid, a sulfur-substituted aminoalkanoicacid, a diaminoalkanol, an aminoalkanediol, a hydroxyl substitutedalkanedioic acid, a hydroxyl substituted aminoalkanoic acid or asulfur-substituted aminoalkanol residue, optionally substituted, whereinthe sulfur substituent is in reduced or oxidized form.

25A. The Antibody Drug Conjugate of any one of embodiments 1A to 23Awherein Le is an amino acid residue of lysine, arginine, asparagine,glutamine, ornithine, citrulline, cysteine, homocysteine, penicillamine,threonine, serine, glutamic acid, aspartic acid, tyrosine, histidine ortryptophan, wherein the amino acid is in the D- or L-configuration.

26A. The Antibody Drug Conjugate of embodiment 24A wherein theaminoalkanedioic acid, diaminoalkanoic acid, sulfur-substitutedaminoalkanoic acid or hydroxyl substituted aminoalkanoic acid residuehas the structure of Formula A or Formula B:

wherein subscript v is an integer ranging from 1 to 4; subscript v′ isan integer ranging from 0 to 4; X^(LP) is selected from the groupconsisting of —O—, —NR^(LP)—, —S—, —S(═O)—, —S(═O)₂—, —C(═O)—,—C(═O)N(R^(LP))—, —N(R^(LP))C(═O)N(R^(LP))—, and—N(R^(LP))C(═NR^(LP))N(R^(LP))— wherein each R^(LP) is independentlyselected from the group consisting of hydrogen and optionallysubstituted alkyl or two of R^(LP) together along with their interveningatoms define a heterocycloalkyl and any remaining R^(LP) are aspreviously defined; Ar is an arylene or heteroarylene, optionallysubstituted; each R^(E) and R^(F) is independently selected from thegroup consisting of —H, optionally substituted alkyl, optionallysubstituted aryl and optionally substituted heteroaryl, or R^(E) andR^(F) together with the same carbon to which they are attached, or R^(E)and R^(F) from adjacent carbons together with these carbons, defines aoptionally substituted cycloalkyl with any remaining R^(E) and R^(F)substituents as previously defined; and wherein the wavy lines indicatescovalent attachment of the Formula A or Formula B structure within theAntibody Drug Conjugate structure.

27A. The Antibody Drug Conjugate of any one of embodiments 1A to 10Awherein -L_(P)(PEG)- has the structure of Formula A1 or A2:

wherein X^(LP) is selected from the group consisting of —O—, —NH, —S—and —C(═O)—; R^(E) and R^(F) are independently selected from the groupconsisting of —H, and —C₁-C₄ alkyl; and wherein the wavy line indicatescovalent attachment of Formula A1 or Formula A2 within the Antibody DrugConjugate structure.

28A. The Antibody Drug Conjugate of embodiment 1A having the structureof:

wherein S is a sulfur atom of the antibody Ligand Unit; R^(2A) ishydrogen or optionally substituted alkyl, or R^(2A) along with theoxygen atom to which it is attached defines an O-linked substituentother than —OH, or R^(2A) is absent when R⁶ is bonded to that oxygenatom, as indicated by the dash curved line, to define anoxygen-containing heterocycloalkyl; the circled Ar represents a5-membered nitrogen-containing heteroarylene, wherein the indicatedrequired substituents to that heteroaryl are in a 1,3-relationship witheach other with optional substitution at the remaining positions; R³ ishydrogen or optionally substituted alkyl; R⁴, R⁵ and R⁶ are optionallysubstituted alkyl, independently selected, or R⁶ is bonded to the oxygenatom of the —OR^(2A) moiety in which R^(2A) is absent and R⁴ and R⁵ areas previously defined; R^(4a) is hydrogen or optionally substitutedalkyl and R^(4B) is optionally substituted alkyl, or both together withthe nitrogen to which they are attached define a nitrogen quaternizedheterocycloalkyl, optionally substituted; one R⁷ is hydrogen oroptionally substituted alkyl and the other R⁷ is optionally substitutedaralkyl or heteroaralkyl; and subscript p is a number ranging from 1 to16.

29A. The Antibody Drug Conjugate of embodiment 28A having the structureof:

wherein subscript m is 0 or 1; subscript p is a number ranging from 1 to8; Z is an optionally alkylene or an optionally substituted alkenylene;and R^(7A) is optionally substituted aryl or optionally substitutedheteroaryl.

30A. The Antibody Drug Conjugate of embodiment 29A having the structureof:

wherein R³ is optionally substituted alkyl; R⁴ is methyl; R⁵ and R⁶ arealkyl side chain residues of natural hydrophobic amino acids,independently selected; subscript p is a number ranging from 1 to 8;subscript u, indicating the number of R^(7B) substituents, is 0, 1, 2 or3; wherein each R^(7B), when present, is an independently selectedO-linked substituent; and R^(8A) is hydrogen or optionally substitutedalkyl.

31A. The Antibody Drug Conjugate of embodiment 30A having the structureis of:

wherein R⁴ is methyl; subscript u is 0, 1 or 2; R³ is H, methyl, ethyl,propyl, —CH₂—OC(O)R^(3A), —CH₂CH(R^(3B))C(O)R^(3A) or—CH(R^(3B))C(O)NHR^(3A), wherein R^(3A) is C₁-C₆ alkyl and R^(3B) is Hor C₁-C₆ alkyl, independently selected from R^(3A); R^(2A) along withthe oxygen atom to which it is attached is an O-linked substituentselected from the group consisting of —OCH₂OCH₂R^(2B), —OCH₂R^(2B),—OC(O)R^(2B), —CH₂OC(O)R^(2A), —OC(O)N(R^(2B))(R^(2C)), and—OCH₂C(O)N(R^(2B))(R^(2C)), wherein R^(2B) and R^(2C) are independentlyselected from the group consisting of H, C₁-C₆ alkyl and C₂-C₆ alkenyl;and each R^(7B), when present, independently is —OH or —OCH₃.

32A. The Antibody Drug Conjugate of embodiment 28A having the structureof:

wherein R^(2A) is hydrogen, an optionally substituted alkyl, saturatedor unsaturated, or R² along with the oxygen atom to which it is attacheddefines an O-linked is substituent other than —OH; R³ is optionallysubstituted C₁-C₆ alkyl; R⁴ is methyl; R⁵ and R⁶ are side chain residuesof natural hydrophobic amino acids, independently selected; and the—N(R^(7′))(R^(7′)) moiety is —NH(C₁-C₆ alkyl) or —NH—N(C₁-C₆ alkyl)₂,wherein one and only one C₁-C₆ alkyl is optionally substituted by —CO₂H,or an ester thereof, or by an optionally substituted phenyl.

33A. The Antibody Drug Conjugate of embodiment 32A wherein the—N(R^(7′))(R^(7′)) moiety is selected from the group consisting of—NH(CH₃), —NHCH₂CH₂Ph, and —NHCH₂—CO₂H, —NHCH₂CH₂CO₂H and—NHCH₂CH₂CH₂CO₂H.

34A. The Antibody Drug Conjugate of embodiment 1A having the structureof:

wherein S is a sulfur atom of the antibody Ligand Unit; the Ab-S— moietyis bonded to the carbon α or β to the indicated M³ carboxylic acid;R^(2A) is hydrogen or optionally substituted alkyl, or R^(2A) along withthe oxygen atom to which it is attached defines an O-linked substituentother than —OH, or R^(2A) is absent when R⁶ is bonded to that oxygenatom to define an oxygen-containing heterocycloalkyl as indicated by thedash curved line; the circled Ar represents a 5-memberednitrogen-heteroarylene, wherein the indicated required substituents tothat heteroarylene are in a 1,3-relationship with each other withoptional substitution at the remaining positions; R³ is hydrogen oroptionally substituted alkyl; R⁴, R⁵ and R⁶ are optionally substitutedalkyl, independently selected, or R6 is bonded to the oxygen atom of the—OR^(2A) moiety in which R^(2A) is absent and R⁴ and R⁵ are aspreviously defined; R^(4a) is hydrogen or optionally substituted alkyland R^(4B) is optionally substituted alkyl, or both together with thenitrogen to which they are attached define a nitrogen quaternizedheterocycloalkyl, optionally substituted; one R⁷ is hydrogen oroptionally substituted alkyl and the other R⁷ is optionally substitutedaralkyl or heteroaralkyl; and subscript p is number ranging from 1 to16.

35A. The Antibody Drug Conjugate of embodiment 31A having the structureof:

wherein subscript m is 0 or 1; Z is an optionally alkylene or anoptionally substituted alkenylene; R² is hydrogen or optionallysubstituted alkyl or R^(2A) along with the oxygen atom to which it isattached defines an O-linked substituent other than —OH; R³ is hydrogenor optionally substituted alkyl; R⁴, R⁵ and R⁶ are optionallysubstituted alkyl, independently selected; and R^(7A) is optionallysubstituted aryl or optionally substituted heteroaryl.

36A. The Antibody Drug Conjugate of embodiment 35A having the structureof:

wherein R³ is optionally substituted alkyl; R⁴ is methyl; R⁵ and R⁶ areside chain residues of natural hydrophobic amino acids, independentlyselected; subscript p′ is an integer ranging from 1 to 8; subscript u,indicating the number of R^(7B) substituents, is 0, 1, 2 or 3, whereineach R^(7B), when present, is an independently selected O-linkedsubstituent; and R^(8A) is hydrogen or optionally substituted alkyl.

37A. The Antibody Drug Conjugate of embodiment 36A having the structureof:

wherein subscript u is 0, 1 or 2; each R^(7B), when present, isindependently —OH or —OCH₃; and R^(2A) is C₁-C₆ alkyl, —CH₂OR^(2B),—CH₂R^(2B), —C(═O)R^(2B), —CH₂C(═O)R^(2B), —C(═O)NHR^(2B) or—CH₂C(═O)NHR^(2B), wherein R^(2B) is C₁-C₆alkyl or C₂-C₆ alkenyl.

38A. The Antibody Drug Conjugate of embodiment 34A having the structureof:

wherein R^(2A) is hydrogen, an optionally substituted alkyl, saturatedor unsaturated, or R² along with the oxygen atom to which it is attacheddefines an O-linked substituent other than —OH; R³ is optionallysubstituted C₁-C₆ alkyl; R⁴ is methyl; R⁵ and R⁶ are side chain residuesof hydrophobic amino acids, preferably natural hydrophic amino acids,independently selected; and the —N(R^(7′))(R^(7′)) moiety is —NH(C₁-C₆alkyl) or —NH—N(C₁-C₆ alkyl)₂, wherein one and only one C₁-C₆ alkyl isoptionally substituted by —CO₂H, or an ester thereof, or by anoptionally substituted phenyl; and subscript p is a number ranging from1 to 8.

39A. The Antibody Drug Conjugate of any one of embodiments 33A to 38Awherein R^(2A) is C₁-C₄, saturated alkyl, C₂-C₄ unsaturated alkyl,—C(═O)R^(2B), wherein R^(2B) is C₁-C₄ alkyl; and subscript p is a numberranging from 1 to 8.

40A. The Antibody Drug Conjugate of embodiment 39A wherein R^(2A) issaturated C₁-C₄ alkyl or unsaturated C₃-C₄ alkyl, wherein saturatedC₁-C₄ alkyl is —CH₃, —CH₂CH₃, —CH₂CH₂CH₃ and unsaturated C₃-C₄ alkyl is—CH₂CH═CH₂ or —CH(CH₃)CH═CH₂.

41A. The Antibody Drug Conjugate of any one of embodiments 1A to 40Awherein L_(P) is an amino acid residue of lysine, arginine, asparagine,glutamine, ornithine, citrulline, cysteine, homocysteine, penicillamine,threonine, serine, glutamic acid, aspartic acid, tyrosine, histidine ortryptophan, wherein the amino acid is in the D- or L-configuration

42A. The Antibody Drug Conjugate of embodiment 31A having the structureof:

wherein A_(O) is absent or is an amine-containing acid residue;subscript p is an number ranging from 1 to 8; subscript q is an integerranging from 1 to 4; subscript u is 0 or 1; subscript v is an integerranging from 1 to 4; R^(7B), when present, is —OH; X^(LP) is selectedfrom the group consisting of —O—, —NH, —S— and —C(═O)—; and R^(E) andR^(F) are independently selected from the group consisting of —H, andC₁-C₄ alkyl; and subscript p is a number ranging from 1 to 8.

43A. The Antibody Drug Conjugate of embodiment 34A having the structureof:

wherein A_(O) is absent or is an amine-containing acid residue;subscript p is a number ranging from 1 to 8; subscript q is an integerranging from 1 to 4; subscript u is 0 or 1; subscript v is an integerranging from 1 to 4; R^(7B), when present, is —OH; X^(LP) is selectedfrom the group consisting of —O—, —NH, —S— and —C(═O)—; and R^(E) andR^(F) are independently selected from the group consisting of —H, and—C₁-C₄ alkyl.

44A. The Antibody Drug Conjugate of any one of embodiments 34A to 41Awherein A is —CH₂(CH₂)₄(C═O)— or —CH₂(CH₂)₄(C═O)NHCH₂CH₂(C═O)—.

45A. The Antibody Drug Conjugate of any one of embodiments 34A to 39A,42A and 43A wherein R^(2A) is —C(O)CH₃.

46A. The Antibody Drug Conjugate of any one of embodiments 34A to 43Awherein R^(2A) is ethyl.

47A. The Antibody Drug Conjugate of any one of embodiments 34A to 43Awherein R^(2A) is —CH₂CH═CH₂.

48A. The Antibody Drug Conjugate of any one of embodiments 34A to 43Awherein A_(O) is a β-amino acid residue.

49A. The Antibody Drug Conjugate of any one of embodiments 1A to 48Awherein PEG has the structure selected from the group consisting of:

wherein the wavy line indicates site of attachment to X^(LP) of theParallel Connector Unit (L_(P)); R^(PEG1) is an optional PEG AttachmentUnit; R^(PEG2) is a PEG Capping Unit; R^(PEG3) is an PEG Coupling Unit;subscript n ranges from 2 to 72; each subscript n′ is independentlyselected from 1 to 72; and subscript e ranges from 2 to 5.

50A. The Antibody Drug Conjugate of embodiment 42A or 43A wherein—X^(LP)-PEG has the structure of:

51A. The Antibody Drug Conjugate of embodiment 50A wherein subscript nis 12 and R^(PEG2) is hydrogen or —CH₃.

52A. The Antibody Drug Conjugate of embodiment 1A having the structureof:

wherein Ab is an antibody Ligand Unit; S is a sulfur atom of theantibody Ligand Unit; the Ab-S— moiety is bonded to the carbon α or β tothe indicated M³ carboxylic acid; subscript u is 0 or 1; R^(7B), whenpresent, is —OH; and R^(2A) along with the oxygen atom to which it isattached is —OC(O)CH₃, CH₂CH₃ or —CH₂CH═CH₂; and p is a number rangingfrom 1 to 8.

53A. A Drug Linker compound wherein the compound has the structure ofFormula 1A or Formula 1C:

or one of Formula IIA-IIF:

wherein L_(B)′ is a Ligand Covalent Binding Unit precursor; L_(P) is aParallel Connector Unit; PEG is a Polyethylene Glycol Unit; subscripts aand b independently are 0 or 1; subscript n is 1, 2, 3 or 4; A is afirst optional Stretcher Unit so that subscript a is 0 when A is absentor 1 when A is present and is optionally comprised of two, three or fourindependently selected subunits (A₁, A₂, A₃, A₄); B is an Branching Unitor a second optional Stretcher Unit (A_(O)) so that subscript b is 0when B is absent or subscript b is 1 when B is present and is optionallycomprised of two, three or four subunits independently of A, whereinsubscript b is 1 and B is a Branching when subscript n is 2, 3 or 4 orsubscript b is 0, or subscript b is 1 so that B is A_(O), when subscriptn is 1; Su is a carbohydrate moiety; —O′— represents an oxygen atom ofan O-glycosidic bond cleavable by a glycosidase; -J′- represents aheteroatom, optionally substituted when nitrogen, from a functionalgroup of B, when B or A_(O) is present, or L_(P), when B or A_(O) isabsent; V, Z¹, Z² and Z³ are ═N— or ═C(R²⁴)—, wherein R²⁴ is hydrogen oralkyl, alkenyl or alkynyl, optionally substituted, or halogen, —NO₂, —CNor other electron withdrawing group, an electron donating group, —O′-Su,or —C(R⁸)(R⁹)-D⁺, wherein at least at least two of V, Z¹, Z² and Z³ are═C(R²⁴)—, provided, one any only one R²⁴ is —C(R⁸)(R⁹)-D⁺ so that—C(R⁸)(R⁹)-D⁺ is bonded to one of V, Z¹, Z², Z³ when that variable groupis ═C(R²⁴)— and one and only one other R²⁴ is so that —O′-Su is bondedto another one of V, Z¹, Z², Z³ when that variable group is ═C(R²⁴)—,and the Q² and —C(R⁸)(R⁹)-D⁺ substituents are ortho or para to eachother; R⁸ and R⁹ independently are hydrogen, alkyl, alkenyl or alkynyl,optionally substituted, or aryl or heteroaryl, optionally substituted;R′ is hydrogen or is halogen, —NO₂, —CN or other electron withdrawinggroup;

D⁺ is a quaternized tubulysin Drug Unit preferably having the structureof:

wherein the circle represents an 5-membered nitrogen-heteroarylene andwherein the indicated required substituents to that heteroarylene are ina 1,3-relationship with each other with optional substitution at theremaining positions; subscript m is 0 or 1; R^(2A) is hydrogen oroptionally substituted alkyl, or R^(2A) along with the oxygen atom towhich it is attached defines an O-linked substituent; R³ is hydrogen oroptionally substituted alkyl; R⁴, R⁵ and R⁶ are optionally substitutedalkyl; one R⁷ is an optionally substituted alkyl, an optionallysubstituted arylalkyl, optionally substituted heteroarylalkyl and theother R⁷ is hydrogen or an optionally substituted alkyl; and R^(8A) ishydrogen or optionally substituted alkyl, wherein the wavy lineindicates covalent bonding of the quaternized tubulysin Drug Unit to theremainder of the Drug Linker compound structures and wherein eachoptionally substituted alkyl is independently selected.

54A. The Drug Linker compound of embodiment 53A wherein —O′-Su has thestructure of Formula 3:

wherein the wavy line represents covalent bonding of O′ to the remainderof the LDC structure; and R⁴⁵ is —CH₂OH or —CO₂H.

55A. The Drug Linker compound of embodiment 54A having the structure ofFormula IV:

wherein J′ is —N(R³³)—, wherein R³³ is hydrogen or methyl; V and Z³independently are ═CH— or ═N—; R′ is hydrogen or an electron withdrawinggroup; R⁸ is hydrogen; R⁹ is hydrogen, optionally substituted C₁-C₆alkyl or optionally substituted phenyl; and R⁴⁵ is —CO₂H.

56A. The Drug Linker compound of embodiment 53A wherein a is 1; andL_(B)′-A- has the structure of Formula V:

wherein the —[C(R^(b1))(R^(b1))]_(q)—[HE]- moiety is A or A₁, wherein A₁is a subunit of A; A₂₋₄ are optional subunits of A; R is hydrogen orC₁-C₄ alkyl; R^(a1) is hydrogen, optionally substituted alkyl or a BasicUnit (BU); and R^(a2) is hydrogen or optionally substituted alkyl, orR^(a1) and R^(a2) together with the carbon atom to which they areattached defines a nitrogen-containing heterocycloalkyl; HE is anoptional Hydrolysis Enhancer (HE) Unit; subscript q is an integerranging from 0 to 6; each R^(b1) independently is hydrogen, optionallysubstituted C₁-C₆ alkyl, optionally substituted aryl or optionallysubstituted heteroaryl, or two R^(b1) together with the carbon(s) towhich they are attached comprise a C₃-C₆ cycloalkyl or one R^(b1) and HEtogether with the carbon to which they are attached define a 5 or6-membered cycloalkyl or a 5- or 6-membered heterocycloalkyl and theother R^(b1) is hydrogen, optionally substituted C₁-C₆ alkyl, optionallysubstituted aryl or optionally substituted heteroaryl; BU has thestructure of —[C(R¹)(R¹)]—[C(R²)(R²)]_(r)—N(R²²)(R²³), or an acidaddition salt thereof, wherein subscript r is 0, 1, 2 or 3; each R¹independently is hydrogen or C₁-C₄ alkyl or two R¹ together with thecarbon to which they are attached comprise a C₃-C₆ cycloalkyl, and eachR² independently is hydrogen, optionally substituted C₁-C₆ alkyl,optionally substituted aryl or optionally substituted heteroaryl, or twoR² together with the carbon(s) to which they are attached and anyintervening carbons define a C₃-C₆ cycloalkyl, or one R¹ and one R²together with the carbons to which they are attached and any interveningcarbons define a 5- or 6-membered cycloalkyl and the remaining R¹ and R²are as defined; R²² and R²³ independently are hydrogen or optionallysubstituted C₁-C₆ alkyl or together with the nitrogen to which they areattached define a 5- or 6-membered heterocycloalkyl, or one of R²², R²³is hydrogen and the other is an acid labile protecting group.

57A. The Drug Linker compound of embodiment 56A wherein Formula V hasthe structure of Formula VA:

wherein subscript q is an integer ranging from 0 to 4.

58A. The Drug linker compound of embodiment 56A wherein Formula V hasthe structure of Formula VB, or an acid addition salt thereof

wherein R²² and R²³ are each hydrogen or one of R²², R²³ is hydrogen andthe other is an acid labile carbamate protecting group; and subscript qis an integer ranging from 0 to 4.

59A. The Drug Linker compound of embodiment 57A or 58A wherein FormulaVA or Formula VB has the structure of:

wherein X⁻ is chloride, acetate, trifluoroacetate or dihydrogenphosphate.

60A. The Drug Linker compound of embodiment 56A having the structure ofFormula VI:

wherein the asterisk (*) designates chirality or absence thereof at theindicated carbon; A₂₋₄ are independently selected optional subunits ofA, wherein —[C(R^(b1))(R^(b1))]_(q)—[HE]- is A₁ when one or more suchsubunits are present; R is hydrogen; R′ is hydrogen or an electronwithdrawing group; R^(a1) is hydrogen or a basic unit (BU) wherein BU isa Basic Unit having the structure of —CH₂—N(R²²)(R²³), or an acidaddition salt thereof, wherein R²² and R²³ independently are hydrogen,methyl or ethyl or both together with the nitrogen atom to which theyare attached comprise a 5- or 6-membered heterocycloalkyl, is or one ofR²², R²³ is hydrogen and the other is an acid labile carbamateprotecting group; R^(a2) is hydrogen; subscript q is an integer rangingfrom 0 to 5 when HE is present or 1 to 5 when HE is absent; each R^(b1)independently is hydrogen or optionally substituted C₁-C₆ alkyl; HE isabsent or is —C(═O)—; R⁴⁵ is —CO₂H; J′ is —NH—; V and Z³ are each ═CH₂—;R⁸ is hydrogen; and R⁹ is hydrogen or methyl.

61A. The Drug Linker compound of embodiment 60A wherein the indicatedstarred (*) carbon is predominantly in the same absolute configurationas the alpha carbon of an L-amino acid when that indicated carbon ischiral.

62A. The Drug Linker compound of any one of embodiments 53A to 61A,wherein A, A_(O), and each of A₂₋₄, when present, independently have thestructure of Formula 7 or Formula 8:

wherein the wavy lines indicated covalent attachment within theremainder of the Drug Linker compound structure, wherein K and Lindependently are C, N, O or S, provided that when K or L is O or S, R⁴¹and R⁴² to K or R⁴³ and R⁴⁴ to L are absent, and when K or L are N, oneof R⁴¹, R⁴² to K or one of R⁴², R⁴³ to L are absent, and provided thatno two adjacent L are independently selected as N, O, or S; whereinsubscripts e and f are independently selected integers that range from 0to 12, and subscript g is an integer ranging from 1 to 12; G ishydrogen, optionally substituted C₁-C₆ alkyl, —OH, —OR^(PR), —CO₂H,CO₂R^(PR), wherein R^(PR) is a suitable protecting, —N(R^(PR))(R^(PR)),wherein R^(PR) are independently a protecting group or R^(PR) togetherform a suitable protecting group, or —N(R⁴⁵)(R⁴⁶), wherein one of R⁴⁵,R⁴⁶ is hydrogen or R^(PR), wherein R^(PR) is a suitable protectinggroup, and the other is hydrogen or optionally substituted C₁-C₆ alkyl;wherein R³⁸ is hydrogen or optionally substituted C₁-C₆ alkyl; R³⁹—R⁴⁴independently are hydrogen, optionally substituted C₁-C₆ alkyl,optionally substituted aryl, or optionally substituted heteroaryl, orboth R³⁹, R⁴⁰ together with the carbon to which they are attachedcomprise a C₃-C₆ cycloalkyl, or R⁴¹, R⁴² together with K to which theyare attached when K is C, or R⁴³, R⁴⁴ together with L to which they areattached when L is a carbon atom comprise a C₃-C₆ cycloalkyl, or R⁴⁰ andR⁴¹, or R⁴⁰ and R⁴³, or R⁴¹ and R⁴³ to together with the carbon atom orheteroatom to which they are attached and the atoms intervening betweenthose carbon atoms and/or heteroatoms comprise a 5- or 6-memberedcycloalkyl or heterocycloalkyl, provided that when K is O or S, R⁴¹ andR⁴² are absent, when K is N, one of R⁴¹, R⁴² is absent, when L is O orS. R⁴³ and R⁴⁴ are absent, and when L is N, one of R⁴³, R⁴⁴ is absent,or wherein A_(O) has a structure corresponding to an alpha-amino,beta-amino or another amine-containing acid.

63A. The Antibody Drug Conjugate of any one of embodiments 53A to 62Awherein D⁺ is a quaternized tubulysin Drug Unit (-D⁺) preferably havingthe structure of

wherein R^(2A) is hydrogen or optionally substituted alkyl, or R^(2A)along with the oxygen atom to which it is attached defines an O-linkedsubstituent other than —OH, or R^(2A) is absent when R⁶ is bonded tothat oxygen atom, as indicated by the curved dash line between R⁶ andthe oxygen atom, to define an oxygen-containing heterocycloalkyl; thecircled Ar represents a 5-membered nitrogen-heteroarylene, wherein theindicated required substituents to that heteroarylene are in a1,3-relationship with each other with optional substitution at theremaining positions; R³ is hydrogen or optionally substituted alkyl; R⁴,R⁵ and R⁶ are optionally substituted alkyl, independently selected, orR⁶ is bonded to the oxygen atom of the —OR^(2A) moiety in which R^(2A)is absent and R⁴ and R⁵ are as previously defined; R^(4a) is hydrogen oroptionally substituted alkyl and R^(4B) is optionally substituted alkyl,or both together with the nitrogen to which they are attached, asindicated by the is curved dotted line between R^(4A) and R^(4B), definea quaternized nitrogen heterocycloalkyl, optionally substituted; one R⁷is hydrogen or optionally substituted alkyl and the other R⁷ isoptionally substituted aralkyl or heteroaralkyl; wherein the wavy lineindicates covalent bonding to the remainder of the Drug Linker compoundstructure.

64A. The Drug Linker compound of embodiment 63A wherein the quaternizedtubulysin Drug Unit -D⁺ has the structure of:

wherein subscript in is 0 or 1; Z is an optionally substituted alkyleneor an optionally substituted alkenylene; and R^(7A) is optionallysubstituted aryl or optionally substituted heteroaryl.

65A. The Drug Linker compound of embodiment 64A wherein the quaternizedtubulysin Drug Unit (-D⁺) has the structure of:

wherein R^(7A) is optionally substituted phenyl and R⁸ is hydrogen ormethyl.

66A. The Drug Linker compound of embodiment 14A wherein the quaternizedtubulysin Drug Unit (-D⁺) has the structure of:

wherein R⁵ and R⁶ are alkyl side chain residues of natural hydrophobicamino acids, independently selected; subscript u, indicating the numberof R^(7B) substituents, is 0, 1, 2 or 3; each R^(7B), when present, isan independently selected O-linked substituent; and R^(8A) is hydrogenor optionally substituted alkyl.

67A. The Drug Linker compound of embodiment 65A wherein the quaternizedtubulysin Drug Unit (-D⁺) has the structure of:

wherein R⁴ is methyl; subscript u is 0, 1 or 2; R³ is H, methyl, ethyl,propyl, —CH₂—OC(O)R^(3A), —CH₂CH(R^(3B))C(O)R^(3A) or—CH(R^(3B))C(O)NHR^(3A), wherein R^(3A) is C₁-C₆ alkyl and R^(3B) is Hor C₁-C₆ alkyl, independently selected from R^(3A); R^(2A) along withthe oxygen atom to which it is attached is an O-linked substituentselected from the group consisting of —OCH₂OCH₂R^(2B), —OCH₂R^(2B),—OC(O)R^(2B), —CH₂OC(O)R^(2B), —OC(O)N(R^(2B))(R^(2C)), and—OCH₂C(O)N(R^(2B))(R^(2C)), wherein R^(2B) and R^(2C) are independentlyselected from the group consisting of H, C₁-C₆ alkyl and C₂-C₆ alkenyl;and each R^(7B), when present, independently is —OH or —OCH₃.

18A. The Drug Linker compound of embodiment 13A wherein the quaternizedtubulysin Drug Unit (-D⁺) has the structure of

wherein R^(2A) is hydrogen, an optionally substituted alkyl, saturatedor unsaturated, or R² along with the oxygen atom to which it is attacheddefines an O-linked substituent other than —OH; R³ is optionallysubstituted C₁-C₆ alkyl; R⁴ is methyl; R⁵ and R⁶ are alkyl side chainresidues of natural hydrophobic amino acids; and the —N(R^(7′))(R^(7′))moiety is —NH(C₁-C₆ alkyl), wherein C₁-C₆ alkyl is optionallysubstituted by —CO₂H, or an ester thereof, or by an optionallysubstituted phenyl, or is —NH—N(C₁-C₆ alkyl)₂, wherein one and only oneC₁-C₆ alkyl is optionally substituted by —CO₂H, or an ester thereof, orby an optionally substituted phenyl.

69A. The Drug Linker compound of embodiment 68A wherein the—N(R^(7′))(R^(7′)) moiety is selected from the group consisting of—NH(CH₃), —NHCH₂CH₂Ph, and —NHCH₂—CO₂H, —NHCH₂CH₂CO₂H and—NHCH₂CH₂CH₂CO₂H.

70A. The Drug Linker compound of any one of embodiments 61A to 68A,wherein R^(2A) is —CH₂CH₃.

71 A. The Drug Linker compound of any one of embodiments, 61A to 68Awherein R^(2A) is —CH₂—CH═CH.

72A. The Drug Linker compound of any one of embodiment 67A or 68Awherein R^(2A) is —CH₂CH₃, —CH₂—CH═CH, or —CH₂C(CH₃)═CH₂, R^(2B) is—CH₃, R³ is —CH₃ and subscript u is 0.

73A. The Drug Linker compound of embodiment 67A or 68A wherein R^(2A) is—CH₂CH₃ or —CH₂—CH═CH₂, or —CH₂C(CH₃)═CH₂, R^(2B) is —CH₃, R³ is —CH₃and subscript u is 1, wherein R^(7B) is —OH.

74A. The Drug Linker compound of any one of embodiments 53A to 73Awherein L_(P) is a aminoalkanedioic acid, a diaminoalkanoic acid, asulfur-substituted alkanedioic acid, a sulfur-substituted aminoalkanoicacid, a diaminoalkanol, an aminoalkanediol, a hydroxyl substitutedalkanedioic acid, a hydroxyl substituted aminoalkanoic acid or asulfur-substituted aminoalkanol residue, optionally substituted, whereinthe sulfur substituent is in reduced or oxidized form.

75A. The Drug Linker compound of any one of embodiments 53A to 73Awherein L_(P) is an amino acid residue of lysine, arginine, asparagine,glutamine, ornithine, citrulline, cysteine, homocysteine, penicillamine,threonine, serine, glutamic acid, aspartic acid, tyrosine, histidine ortryptophan, wherein the amino acid is in the D- or L-configuration.

76A. The Drug Linker compound of embodiment 74A wherein theaminoalkanedioic acid, diaminoalkanoic acid, sulfur-substitutedaminoalkanoic acid or hydroxyl substituted aminoalkanoic acid residuehas the structure of Formula A or Formula B:

wherein subscript v is an integer ranging from 1 to 4; subscript v′ isan integer ranging from 0 to 4; X^(LP) is selected from the groupconsisting of —O—, —NR^(LP)—, —S—, —S(═O)—, —S(═O)₂—, —C(═O)—,—C(═O)N(R^(LP))—, —N(R^(LP))C(═O)N(R^(LP))—, and—N(R^(LP))C(═NR^(LP))N(R^(LP))— wherein each R^(LP) is independentlyselected from the group consisting of hydrogen and optionallysubstituted alkyl or two of R^(LP) together along with their interveningatoms define a heterocycloalkyl and any remaining R^(LP) are aspreviously defined; Ar is an arylene or heteroarylene, optionallysubstituted; each R^(E) and R^(F) is independently selected from thegroup consisting of —H, optionally substituted alkyl, optionallysubstituted aryl and optionally substituted heteroaryl, or R^(E) andR^(F) together with the same carbon to which they are attached, or R^(E)and R^(F) from adjacent carbons together with these carbons, defines aoptionally substituted cycloalkyl with any remaining R^(E) and R^(F)substituents as previously defined; and wherein the wavy lines indicatescovalent attachment of the Formula A or Formula B structure within theDrug Linker compound structure.

77A. The Drug Linker compound of any one of embodiments 53A to 60Awherein -L_(P)(PEG)- has the structure of Formula A1 or A2:

wherein X^(LP) is selected from the group consisting of —O—, —NH, —S—and —C(═O)—; R^(E) and R^(F) are independently selected from the groupconsisting of —H, and —C₁-C₄ alkyl; and wherein the wavy line indicatescovalent attachment of Formula A1 or Formula A2 within the Drug Linkercompound structure.

78A. The Drug Linker compound of embodiment 1A having the structure of:

wherein R^(2A) is hydrogen or optionally substituted alkyl, or R^(2A)along with the oxygen atom to which it is attached defines an O-linkedsubstituent other than —OH, or R^(2A) is absent when R⁶ is bonded tothat oxygen atom, as indicated by the dash curved line, to define anoxygen-containing heterocycloalkyl; the circled Ar represents a5-membered nitrogen-containing heteroarylene, wherein the indicatedrequired substituents to that heteroaryl are in a 1,3-relationship witheach other with optional substitution at the remaining positions; R³ ishydrogen or optionally substituted alkyl; R⁴, R⁵ and R⁶ are optionallysubstituted alkyl, independently selected, or R⁶ is bonded to the oxygenatom of the —OR^(2A) moiety in which R^(2A) is absent and R⁴ and R⁵ areas previously defined; R^(4a) is hydrogen or optionally substitutedalkyl and R^(4B) is optionally substituted alkyl, or both together withthe nitrogen to which they are attached define a nitrogen quaternizedheterocycloalkyl, optionally substituted; and one R⁷ is hydrogen oroptionally substituted alkyl and the other R⁷ is optionally substitutedaralkyl or heteroaralkyl.

79A. The Drug Linker compound of embodiment 78A having the structure of:

wherein subscript m is 0 or 1; subscript p is a number ranging from 1 to8; Z is an optionally alkylene or an optionally substituted alkenylene;and R^(7A) is optionally substituted aryl or optionally substitutedheteroaryl.

80A. The Drug Linker compound of embodiment 79A having the structure of:

R³ is optionally substituted alkyl; R⁴ is methyl; R⁵ and R⁶ are alkylside chain residues of hydrophobic amino acids, preferably naturalhydrophobic amino acids, independently selected; subscript p is a numberranging from 1 to 8; subscript u, indicating the number of R^(7B)substituents, is 0, 1, 2 or 3; wherein each R^(7B), when present, is anindependently selected O-linked substituent; and R^(8A) is hydrogen oroptionally substituted alkyl.

81A. The Drug Linker compound of embodiment 80A having the structure of:

wherein R⁴ is methyl; subscript u is 0, 1 or 2; R³ is 1H, methyl, ethyl,propyl, —CH₂—OC(O)R^(3A), —CH₂CH(R^(3B))C(O)R^(3A) or—CH(R^(3B))C(O)NHR^(3A), wherein R^(3A) is C₁-C₆ alkyl and R^(3B) is Hor C₁-C₆ alkyl, independently selected from R^(3A); R^(2A) along withthe oxygen atom to which it is attached is an O-linked substituentselected from the group consisting of —OCH₂OCH₂R^(2B), —OCH₂R^(2B),—OC(O)R^(2B), —CH₂OC(O)R^(2B), —OC(O)N(R^(2B))(R^(2C)), and—OCH₂C(O)N(R^(2B))(R^(2C)), wherein R^(2B) and R^(2C) are independentlyselected from the group consisting of H, C₁-C₆ alkyl and C₂-C₆ alkenyl;and each R^(7B), when present, independently is —OH or —OCH₃.

82A. The Drug Linker compound of embodiment 78A having the structure of:

wherein R^(2A) is hydrogen, an optionally substituted alkyl, saturatedor unsaturated, or R² along with the oxygen atom to which it is attacheddefines an O-linked substituent other than —OH; R³ is optionallysubstituted C₁-C₆ alkyl; R⁴ is methyl; R⁵ and R⁶ are side chain residuesof hydrophobic amino acids, preferably natural hydrophobic amino acids,independently selected; and the —N(R^(7′))(R^(7′)) moiety is —NH(C₁-C₆alkyl), wherein C₁-C₆ alkyl is optionally substituted by —CO₂H, or anester thereof, or by an optionally substituted phenyl, or is —NH—N(C₁-C₆alkyl)₂, wherein one and only one C₁-C₆ alkyl is optionally substitutedby —CO₂H, or an ester thereof, or by an optionally substituted phenyl.

83A. The Drug Linker compound of embodiment 82A wherein the—N(R^(7′))(R^(7′)) moiety is selected from the group consisting of—NH(CH₃), —NHCH₂CH₂Ph, and —NHCH₂—CO₂H, —NHCH₂CH₂CO₂H and—NHCH₂CH₂CH₂CO₂H.

84A. The Drug Linker compound of any one of embodiments 72A to 83Awherein R^(2A) is C₁-C₄, saturated alkyl, C₂-C₄ unsaturated alkyl,—C(═O)R^(2B), wherein R^(2B) is C₁-C₄ alkyl.

85A. The Drug Linker compound of embodiment 84A wherein R^(2A) issaturated C₁-C₄ alkyl or unsaturated C₃-C₄ alkyl, wherein saturatedC₁-C₄ alkyl is —CH₃, —CH₂CH₃, —CH₂CH₂CH₃ and unsaturated C₃-C₄ alkyl is—CH₂CH═CH₂ or —CH(CH₃)CH═CH₂.

86A. The Drug Linker compound of any one of embodiments 53A to 85Awherein L_(P) is an amino acid residue of lysine, arginine, asparagine,glutamine, ornithine, citrulline, cysteine, homocysteine, penicillamine,threonine, serine, glutamic acid, aspartic acid, tyrosine, histidine ortryptophan, wherein the amino acid is in the D- or L-configuration.

87A. The Drug Linker compound of embodiment 81A having the structure of:

wherein A_(O) is absent or is an amine-containing acid residue;subscript p is an number ranging from 1 to 8; subscript q is an integerranging from 1 to 4; subscript u is 0 or 1; subscript v is an integerranging from 1 to 4; R^(7B), when present, is —OH; X^(LP) is selectedfrom the group consisting of —O—, —NH—, —S— and —C(═O)—; and R^(E) andR^(F) are independently selected from the group consisting of —H, andC₁-C₄ alkyl.

88A. The Drug Linker compound of embodiment 81 A having the structureof:

wherein A_(O) is absent or is an amine-containing acid residue;subscript, q is an integer ranging from 1 to 4; subscript u is 0 or 1;subscript v is an integer ranging from 1 to 4; R^(7B), when present, is—OH; X^(LP) is selected from the group consisting of —O—, —NH, —S— and—C(═O)—; and R^(E) and R^(F) are independently selected from the groupconsisting of —H, and —C₁-C₄ alkyl.

89A. The Drug linker compound of any one of embodiments 73A to 86Awherein A is —CH₂(CH₂)₄(C═O)— or —CH₂(CH₂)₄(C═O)NHCH₂CH₂(C═O)—.

89A. The Drug linker compound of any one of embodiments 78A to 84A, 87Aand 88A wherein R^(2A) is —C(═O)CH₃.

90A. The Drug linker compound of any one of embodiments 78A to 88Awherein R^(2A) is ethyl.

91A. The Drug linker compound of any one of embodiments 78A to 88Awherein R^(2A) is —CH₂CH═CH₂.

92A. The Drug linker compound of any one of embodiments 78A to 87Awherein A_(O) is a β-amino acid residue.

93A. The Drug linker compound of any one of embodiments 53A to 92Awherein PEG has the structure selected from the group consisting of:

wherein the wavy line indicates site of attachment to X^(LP) of theParallel Connector Unit (L_(P)); R^(PEG1) is an optional PEG AttachmentUnit; R^(PEG2) is a PEG Capping Unit; R^(PEG3) is an PEG Coupling Unit;subscript n ranges from 2 to 72: each subscript n′ is independentlyselected from 1 to 72; and subscript e ranges from 2 to 5.

94A. The Drug linker compound of embodiment 87A or 88A wherein—X^(LP)—PEG has the structure of:

95A. The Drug linker compound of embodiment 94A wherein subscript n is12 and R^(PEG2) is hydrogen or —CH₃.

96A. The Drug linker compound of embodiment 53 having the structure of:

wherein subscript u is 0 or 1; R^(7B), when present, is —OH; and R^(2A)along with the oxygen atom to which it is attached is —OC(O)CH₃, CH₂CH₃or —CH₂CH═CH₂.

1B. A Ligand Drug Conjugate composition, wherein the composition isrepresented b the structure of Formula 1:

wherein L a Ligand Unit from a targeting agent, wherein L selectivelybinds to a targeted moiety; L_(B) is a Ligand Covalent Binding Unit;L_(P) is a Parallel Connector Unit; PEG is a Polyethylene Glycol Unit;subscripts a and b independently are 0 or 1; subscript n is 1, 2, 3 or4; A is a first optional Stretcher Unit so that subscript a is 0 when Ais absent or 1 when A is present and is optionally comprised of two,three or four independently selected subunits (A₁, A₂, A₃, A₄); B is anBranching Unit or a second optional Stretcher Unit (A_(O)) so thatsubscript b is 0 when B is absent or 1 when B is present and isoptionally comprised of two, three or four subunits independently of A,wherein subscript b is 1 and B is a Branching when subscript n is 2, 3or 4 or b is 0 or 1 so that B is A_(O) when subscript n is 1; Su is acarbohydrate moiety; —O′— represents an oxygen atom of an O-glycosidicbond cleavable by a glycosidase; -J′- represents a heteroatom,optionally substituted when nitrogen, from a functional group of B, whenB is present, or L_(B), when B is absent; V, Z¹, and Z² is ═N— or═C(R²⁴)—, wherein R²⁴ is hydrogen or alkyl, alkenyl or alkynyl,optionally substituted, or halogen, —NO₂, —CN or other electronwithdrawing group, an electron donating group. —O′-Su, or —C(R⁸)(R⁹)-D⁺,wherein at least at least two of V, Z¹ and Z² are ═C(R²⁴)—, provided,one any only one R²⁴ is —C(R⁸)(R⁹)-D⁺ so that —C(R⁸)(R⁹)-D⁺ is bonded toone of V, Z¹, Z² when that variable group is ═C(R²⁴)— and one and onlyone other R²⁴ is so that —O′-Su is bonded to another one of V, Z¹, Z²when that variable group is ═C(R²⁴)—, and the —O′-Su and —C(R⁸)(R⁹)-D⁺substituents are ortho or para to each other; R⁸ and R⁹ independentlyare hydrogen, alkyl, alkenyl or alkynyl, optionally substituted, or arylor heteroaryl, optionally substituted; R′ is hydrogen or is halogen,—NO₂, —CN or other electron withdrawing group; D⁺ is a quaternizedtubulysin Drug Unit; subscript p is an average drug loading having anumber ranging from 1 to 24; and wherein said glycosidase cleavageresults in release of a tubulysin compound (D) from a Ligand DrugConjugate compound of the composition. 2B. The Ligand Drug Conjugatecomposition of embodiment 1B wherein the quaternized tubulysin Drug Unit(-D⁺) has the structure of:

wherein the circle represents an 5-membered nitrogen-heteroarylene andwherein the indicated required substituents to that heteroarylene are ina 1,3-relationship with each other with optional substitution at theremaining positions; subscript m is 0 or 1; R^(2A) is hydrogen oroptionally substituted alkyl, or R^(2A) along with the oxygen atom towhich it is attached defines an O-linked substituent; R³ is hydrogen oroptionally substituted alkyl; R⁴, R⁵ and R⁶ are optionally substitutedalkyl; one R⁷ is an optionally substituted alkyl, an optionallysubstituted arylalkyl, optionally substituted heteroarylalkyl and theother R⁷ is hydrogen or an optionally substituted alkyl; and R^(8A) ishydrogen or optionally substituted alkyl, wherein the wavy lineindicates covalent bonding of D⁺ to the remainder of the Conjugatestructure and wherein each optionally substituted alkyl is independentlyselected.

3B. The Ligand Drug Conjugate composition of embodiment 2B wherein thecomposition is represented by the structure of one of Formula 2C, 2D, 2Eand 2F:

4B. The Ligand Drug Conjugate composition of embodiment 3B wherein thetargeting agent is an antibody, thereby defining an antibody drugconjugate (ADC) so that L is an antibody Ligand Unit, wherein thetargeted moiety of the antibody Ligand Unit is an accessiblecell-surface antigen of targeted abnormal or other unwanted cells thatis capable of cellular internalization of bound ADC, wherein the antigenis preferentially present on the abnormal or other unwanted cells incomparison to normal cells.

5B. The Ligand Drug Conjugate composition of embodiment 3B wherein thetargeting agent is a cognate ligand of an accessible cell-surfacereceptor and the targeted moiety is that cell-surface receptor, whereinthe targeted receptor on abnormal cells or other unwanted cells iscapable of cellular internalization of bound LDC, and wherein thereceptor is preferentially present on the abnormal cells in comparisonto normal cells.

6B. The Ligand Drug Conjugate composition of embodiment 3B wherein thetargeting agent is an antibody, thereby defining an antibody drugconjugate (ADC), wherein the targeted moiety of the antibody Ligand Unitis an accessible cell-surface antigen of a vascular epithelial cell inthe vicinity of abnormal cells or other unwanted cells, wherein saidantigen is more abundant on said cells in comparison to epithelial cellsin the periphery and is capable of cellular internalization of boundADC.

7B. The Ligand Drug Conjugate composition of any one of embodiments 1Bto 6B wherein —O′-Su has the structure of Formula 3:

wherein the wavy line represents covalent bonding of O′ to the remainderof the LDC structure; and R⁴⁵ is —CH₂OH or —CO₂H.

8B. The Ligand Drug Conjugate composition of embodiment 7B wherein thecomposition is represented b the structure of Formula 4

wherein Ab is an antibody Ligand Unit; J′ is —N(R³³)—, wherein R³³ ishydrogen or methyl; V is ═CH— or ═N—; R′ is hydrogen or an electronwithdrawing group; R⁸ is hydrogen; R⁹ is hydrogen, optionallysubstituted C₁-C₆ alkyl or optionally substituted phenyl; R⁴⁵ is —CO₂H;and subscript p is a number ranging from 1 to 24.

9B. The Ligand Drug Conjugate composition of embodiment 1B whereinsubscript a is 1; and -L_(B)-A- of Formula 1 has the structure ofFormula 5

wherein the —[C(R^(b1))(R^(b1))]—[HE]- moiety is A or A₁, wherein A₁ isa subunit of A; A₂₋₄ are optional subunits of A; R is hydrogen or C₁-C₄alkyl; R^(a1) is hydrogen, optionally substituted alkyl or a Basic Unit(BU); and R^(a2) is hydrogen or optionally substituted alkyl, or R^(a1)and R^(a2) together with the carbon atom to which they are attacheddefines a nitrogen-containing heterocycloalkyl; HE is an optionalHydrolysis Enhancer (HE) Unit; subscript q is an integer ranging from 0to 6; each R^(b1) independently is hydrogen, optionally substitutedC₁-C₆ alkyl, optionally substituted aryl or optionally substitutedheteroaryl, or two R^(b1) together with the carbon(s) to which they areattached comprise a C₃-C₆ cycloalkyl or one R^(b1) and HE together withthe carbon to which they are attached define a 5 or 6-memberedcycloalkyl or a 5- or 6-membered heterocycloalkyl and the other R^(b1)is hydrogen, optionally substituted C₁-C₆ alkyl, optionally substitutedaryl or optionally substituted heteroaryl; BU has the structure of—[C(R¹)(R¹)]—[C(R²)(R²)], —N(R²²)(R²³), or an acid addition saltthereof, wherein subscript r is 0, 1, 2 or 3; each R¹ independently ishydrogen or lower alkyl or two R¹ together with the carbon to which theyare attached comprise a C₃-C₆ cycloalkyl, and each R² independently ishydrogen, optionally substituted C₁-C₆ alkyl, optionally substitutedaryl or optionally substituted heteroaryl, or two R² together with thecarbon(s) to which they are attached and any intervening carbons definea C₃-C₆ cycloalkyl, or one R¹ and one R² together with the carbons towhich they are attached and any intervening carbons define a 5- or6-membered cycloalkyl and the remaining R¹ and R² are as defined; R²²and R²³ independently are hydrogen or optionally substituted C₁-C₆ alkylor together with the nitrogen to which they are attached define a 5- or6-membered heterocycloalkyl, or one of R²², R²³ is hydrogen and theother is an acid labile protecting group; and wherein the dotted line isan optional double bond and the wavy line to the succinimide (doublebond is absent) or maleimide ring (double bond is present) of L_(B)indicates covalent bonding of sulfur derived from a sulfhydryl group ofa targeting moiety and the other wavy line indicates covalent bonding ofthe Formula 4 structure to the remainder of the LDC structure.

10B. The Ligand Drug Conjugate composition of embodiment 9B whereinFormula 5 has the structure of Formula 5A:

wherein subscript q is an integer ranging from 0 to 4.

11B. The Ligand Drug Conjugate composition of embodiment 9B whereinFormula 4 has the structure of Formula 5B, or an acid addition saltthereof

wherein R²² and R²³ are each hydrogen or one of R²², R²³ is hydrogen andthe other is an acid labile carbamate protecting group; and subscript qis an integer ranging from 0 to 4.

12B. The Ligand Drug Conjugate composition of embodiment 10B or 11Bwherein Formula 5A or Formula 5B has the structure of:

wherein X⁻ is chloride, acetate, trifluoroacetate or dihydrogenphosphate.

13B. The Ligand Drug Conjugate composition of embodiment 9B wherein thecomposition is represented by the structure of Formula 6:

wherein Ab is an antibody Ligand Unit. S is a sulfur atom of theantibody Ligand Unit; the asterisk (*) designates chirality or absencethereof at the indicated carbon; A₂₋₄ are independently selectedoptional subunits of A, wherein —[C(R^(b1))(R^(b1))]_(q)—[HE]- is A₁when one or more such subunits are present: R is hydrogen; R′ ishydrogen or an electron withdrawing group; R^(a1) is hydrogen or a basicunit (BU) wherein BU is a Basic Unit having the structure of—CH₂—N(R²²)(R²³), or an acid addition salt thereof, wherein R²² and R²³independently are hydrogen, methyl or ethyl or both together with thenitrogen atom to which they are attached comprise a 5- or 6-memberedheterocycloalkyl, or one of R²², R²³ is hydrogen and the other is anacid labile carbamate protecting group; R^(a2) is hydrogen; subscript qis an integer ranging from 0 to 5 when HE is present or 1 to 5 when HEis absent; each R^(b1) independently is hydrogen or optionallysubstituted C₁-C₆ alkyl; HE is absent or is —C(═O)—; R⁴⁵ is —CO₂H; J′ is—NH—; V and Z³ are ═CH₂—; R⁸ is hydrogen; R⁹ is hydrogen or methyl; andsubscript p is a number ranging from 1 to 16.

14B. The Ligand Drug Conjugate composition of embodiment 1B whereincompounds of the composition are independently represented by thestructure of Formula 9A or Formula 9B:

wherein Ab is an antibody Ligand Unit; S is a sulfur atom of theantibody Ligand Unit; A₂₋₄ are independently selected optional subunitsof A, wherein —[C(R^(b1))(R^(b1))]_(q)—[HE]- is A₁ when one or more suchsubunits are present; R is hydrogen; R′ is hydrogen or an electronwithdrawing group; R^(a1) is —H or BU wherein BU is a Basic Unit havingthe structure of —CH₂—N(R²²)R²³), or an acid addition salt thereof,wherein R²² and R²³ independently are hydrogen or methyl or bothtogether with the nitrogen atom to which they are attached define abasic nitrogen-containing 5- or 6-membered heterocycloalkyl, or one ofR²², R²³ is hydrogen and the other is an acid labile protecting group;R^(a2) is hydrogen; subscript q is an integer ranging from 0 to 5 whenHE is present or from 1 to 5 when HE is absent; each R^(b1)independently is hydrogen or optionally substituted C₁-C₆ alkyl; HE isabsent or is —C(═O)—; J′ is —O— or —NH—; R⁸ and R⁹ are independently —Hor optionally substituted alkyl or both together along with the carbonatom to which they are attached define a cycloalkyl; and subscript p′ isan integer ranging from 1 to 24.

15B. The Ligand Drug Conjugate composition of embodiment 14B whereincompounds of the composition are independently represented by thestructure of Formula 10A or Formula 10B:

wherein R is hydrogen; R′ is hydrogen, —NO₂, —Cl or —F; HE is —C(═O)—;R⁴⁵ is —CO₂H; J′ is —NH—; V is ═CH₂—; R⁸ is hydrogen; and R⁹ is hydrogenor methyl.

16B. The Ligand Drug Conjugate composition of embodiment 13B, 14B or 15Bwherein the indicated starred (*) carbon is predominantly in the sameabsolute configuration as the alpha carbon of an L-amino acid when thatindicated carbon is chiral.

17B. The Ligand Drug Conjugate composition of any one of embodiment 1Bto 8B wherein A and A_(O), when present, or any one of embodiments 9B to16B, wherein each of A₂₋₄, when present, independently have thestructure of Formula 7 or Formula 8

wherein the wavy lines indicate covalent attachment within the remainderof L_(O), wherein K and L independently are C, N, O or S, provided thatwhen K or L is O or S, R⁴¹ and R⁴² to K or R⁴¹ and R⁴⁴ to L are absent,and when K or L are N, one of R⁴¹, R⁴² to K or one of R⁴², R⁴³ to L areabsent, and provided that no two adjacent L are independently selectedas N, O, or S; wherein subscripts e and f are independently selectedintegers that range from 0 to 12, and subscript g is an integer rangingfrom 1 to 12; wherein G is hydrogen, optionally substituted C₁-C₆ alkyl,—OH, —OR^(PR), —CO₂H, CO₂R^(PR), wherein R^(PR) is a suitableprotecting, —N(R^(PR))(R^(PR)), wherein R^(PR) are independently aprotecting group or R^(PR) together form a suitable protecting group, or—N(R⁴⁵)(R⁴⁶), wherein one of R⁴⁵, R⁴⁶ is hydrogen or R^(PR), whereinR^(PR) is a suitable protecting group, and the other is hydrogen oroptionally substituted C₁-C₆ alkyl; wherein R³⁸ is hydrogen oroptionally substituted C₁-C₆ alkyl; R³⁹—R⁴⁴ independently are hydrogen,optionally substituted C₁-C₆ alkyl, optionally substituted aryl, oroptionally substituted heteroaryl, or both R³⁹, R⁴⁰ together with thecarbon to which they are attached comprise a C₃-C₆ cycloalkyl, or R⁴¹,R⁴² together with K to which they are attached when K is C, or R⁴³, R⁴⁴together with L to which they are attached when L is a carbon atomcomprise a C₃-C₆ cycloalkyl, or R⁴⁰ and R⁴¹, or R⁴⁰ and R⁴³, or R⁴¹ andR⁴³ to together with the carbon atom or heteroatom to which they areattached and the atoms intervening between those carbon atoms and/orheteroatoms comprise a 5- or 6-membered cycloalkyl or heterocycloalkyl,provided that when K is O or S, R⁴¹ and R⁴² are absent, when K is N, oneof R⁴¹, R⁴² is absent, when L is O or S, R⁴³ and R⁴⁴ are absent, andwhen L is N, one of R⁴³, R⁴⁴ is absent, or wherein A_(O) has a structurecorresponding to alpha-amino, beta-amino or another amine-containingacid.

18B. The Ligand Drug Conjugate composition of any one of embodiments 1Bto 17B wherein the quaternized tubulysin Drug Unit -D⁺ has the structureof

R^(2A) is hydrogen or optionally substituted alkyl, or R^(2A) along withthe oxygen atom to which it is attached defines an O-linked substituentother than —OH, or R^(2A) is absent when R⁶ is bonded to that oxygenatom, as indicated by the curved dash line between R⁶ and the oxygenatom, to define an oxygen-containing heterocycloalkyl; the circled Arrepresents a 5-membered nitrogen-heteroarylene, wherein the indicatedrequired substituents to that heteroarylene are in a 1,3-relationshipwith each other with optional substitution at the remaining positions;R³ is hydrogen or optionally substituted alkyl; R⁴, R⁵ and R⁶ areoptionally substituted alkyl, independently selected, or R⁶ is bonded tothe oxygen atom of the —OR^(2A) moiety in which R^(2A) is absent and R⁴and R⁵ are as previously defined; R^(4a) is hydrogen or optionallysubstituted alkyl and R^(4B) is optionally substituted alkyl, or bothtogether with the nitrogen to which they are attached, as indicated bythe curved dotted line between R^(4A) and R^(4B), define a quaternizednitrogen heterocycloalkyl, optionally substituted; one R⁷ is hydrogen oroptionally substituted alkyl and the other R⁷ is optionally substitutedaralkyl or heteroaralkyl; wherein the wavy line indicates covalentbonding of the D⁺ structure to the remainder of the LDC structure.

19B. The Ligand Drug Conjugate composition of embodiment 18B wherein thequaternized tubulysin Drug Unit -D⁺ has the structure of:

wherein subscript m is 0 or 1; Z is an optionally substituted alkyleneor an optionally substituted alkenylene; and R^(7A) is optionallysubstituted aryl or optionally substituted heteroaryl.

20B. The Ligand Drug Conjugate composition of embodiment 19B wherein thequaternized tubulysin Unit -D⁺ has the structure of:

wherein R^(7A) is optionally substituted phenyl and R⁸ is hydrogen ormethyl.

21B. The Ligand Drug Conjugate composition of embodiment 19B wherein thequaternized tubulysin Drug Unit -D⁺ has the structure of:

wherein R⁵ and R⁶ are alkyl side chain residues of natural hydrophobicamino acids, independently selected; subscript u, indicating the numberof R^(7B) substituents, is 0, 1, 2 or 3; each R^(7B), when present, isan independently selected O-linked substituent; and R^(8A) is hydrogenor optionally substituted alkyl.

22B. The Ligand Drug Conjugate composition of embodiment 21B wherein thequaternized tubulysin Drug Unit (-D⁺) has the structure of:

wherein R⁴ is methyl; subscript u is 0, 1 or 2; R³ is H, methyl, ethyl,propyl, —CH₂—OC(O)R^(3A), —CH₂CH(R^(3B))C(O)R^(3A) or—CH(R^(3B))C(O)NHR^(3A), wherein R is C₁-C₆ alkyl and R^(3B) is H orC₁-C₆ alkyl, independently selected from R^(3A); R^(2A) along with theoxygen atom to which it is attached is an O-linked substituent selectedfrom the group consisting of —OCH₂OCH₂R^(2B), —OCH₂R^(2B), —OC(O)R^(2B),—CH₂OC(O)R^(2B), —OC(O)N(R^(2B))(R^(2C)), and—OCH₂C(O)N(R^(2B))(R^(2C)), wherein R^(2B) and R^(2C) are independentlyselected from the group consisting of H, C₁-C₆ alkyl and C₂-C₆ alkenyl;and each R^(7B), when present, independently is —OH or —OCH₃.

23B. The Ligand Drug Conjugate composition of embodiment 18B wherein thequaternized tubulysin Drug Unit (-D⁺) has the structure of

wherein R^(2A) is hydrogen, an optionally substituted alkyl, saturatedor unsaturated, or R² along with the oxygen atom to which it is attacheddefines an O-linked substituent other than —OH; R³ is optionallysubstituted C₁-C₆ alkyl; R⁴ is methyl; R⁵ and R⁶ are alkyl side chainresidues of natural hydrophobic amino acids; and the —N(R^(7′))(R^(7′))moiety is —NH(C₁-C₆ alkyl) or —NH—N(C₁-C₆ alkyl)₂, wherein one and onlyone C₁-C₆ alkyl is optionally substituted by —CO₂H, or an ester thereof,or by an optionally substituted phenyl.

24B. The Ligand Drug Conjugate composition of embodiment 23B wherein the—N(R^(7′))(R^(7′)) moiety is selected from the group consisting of—NH(CH₃), —NHCH₂CH₂Ph, and —NHCH₂—CO₂H, —NHCH₂CH₂CO₂H and—NHCH₂CH₂CH₂CO₂H.

25B. The Ligand Drug Conjugate composition of any one of claims 18B to24B wherein R^(2A) is —CH₂CH₃.

26B. The Ligand Drug Conjugate composition of any one of claims 18B to24B wherein R^(2A) is —CH₂—CH═CH₂.

27B. The Ligand Drug Conjugate composition of any one of claim 21B or22B wherein R^(2A) is —CH₂CH₃, —CH₂—CH═CH₂ or —CH₂C(CH₃)═CH₂, R^(2B) is—CH₃, R³ is —CH₃ and subscript u is 0.

28B. The Ligand Drug Conjugate composition of claim 21B or 22B whereinR^(2A) is —CH₂CH₃ or —CH₂—CH═CH₂, or —CH₂C(CH₃)═CH₂, R^(2B) is —CH₃, R³is —CH₃ and subscript u is 1, wherein R^(7B) is —OH.

29B. The Ligand Drug Conjugate composition of embodiment 18B wherein thequaternized tubulysin Drug Unit (-D⁺) has the structure of:

wherein R^(2B) is —CH₃, —CH₂CH₃, —CH₂CH₂CH₃, —CH(CH₃)₂, —CH₂CH(CH₃)₂, or—CH₂C(CH₃)₃.

30B. The Ligand Drug Conjugate composition of embodiment 18B wherein thequaternized tubulysin Drug Unit (-D⁺) has the structure of:

wherein R^(2B) is hydrogen, methyl or —OCH₃, or —OCH₂R^(2B) is—OCH₂CH—CH₂ or —OCH₂C(CH₃)═CH₂.

31B. The Ligand Drug Conjugate composition of embodiment 18B wherein thequaternized tubulysin Drug Unit (-D⁺) is that of tubulysin M, for whichD⁺ has the structure of:

32B. The Ligand Drug Conjugate composition of embodiment 1B representedby the structure of:

1C. A Ligand Drug Conjugate composition wherein the composition isrepresented by the structure of Formula 1A or Formula 1C:

wherein L is an antibody Ligand Unit, thereby defining an Antibody DrugConjugate (ADC); L_(B) is a Ligand Covalent Binding Unit; L_(P) is aParallel Connector Unit; PEG is a Polyethylene Glycol Unit; subscripts aand b independently are 0 or 1; subscript n is 1, 2, 3 or 4; subscript pis a number ranging from 1 to 24; A is a first optional Stretcher Unitso that subscript a is 0 when A is absent or 1 when A is present and isoptionally comprised of two, three or four independently selectedsubunits (A₁, A₂, A₃, A₄); B is an Branching Unit or a second optionalStretcher Unit (A_(O)) so that subscript b is 0 when B is absent or 1when B is present and is optionally comprised of two, three or foursubunits independently of A, wherein subscript b is 1 and B is aBranching when subscript n is 2, 3 or 4 or b is 0 or 1 so that B isA_(O) when subscript n is 1; Su is a carbohydrate moiety; —O′—represents an oxygen atom of an O-glycosidic bond cleavable by aglycosidase; -J′- represents a heteroatom, optionally substituted whennitrogen, from a functional group of B, when B is present, or L_(B),when B is absent; V, Z¹, Z² and Z³ are ═N— or ═C(R²⁴)—, wherein R²⁴ ishydrogen or alkyl, alkenyl or alkynyl, optionally substituted, orhalogen, —NO₂, —CN or other electron withdrawing group, or —OCH₃ orother electron donating group, —O′-Su, or —C(R⁸)(R⁹)-D⁺, wherein atleast at least two of V, Z¹, Z² and Z³ are ═C(R²⁴)—, provided, one anyonly one R²⁴ is —C(R⁸)(R⁹)-D⁺ so that —C(R⁸)(R⁹)-D⁺ is bonded to one ofV, Z¹, Z², Z³ when that variable group is ═C(R²⁴)— and one and only oneother R²⁴ is so that —O′-Su is bonded to another one of V, Z¹, Z¹, Z³when that variable group is ═C(R²⁴)—, and the —O′Su and —C(R⁸)(R⁹)-D⁺substituents are ortho or para to each other; R⁴ and R⁹ independentlyare hydrogen, alkyl, alkenyl or alkynyl, optionally substituted, or arylor heteroaryl, optionally substituted; R′ is hydrogen or is halogen,—NO₂, —CN or other electron withdrawing group; D⁺ is a quaternizedtubulysin Drug Unit having the structure of:

wherein the circle represents an 5-membered nitrogen-heteroarylene andwherein the indicated required substituents to that heteroarylene are ina 1,3-relationship with each other with optional substitution at theremaining positions; subscript m is 0 or 1; R^(2A) is hydrogen oroptionally substituted alkyl, or R^(2A) along with the oxygen atom towhich it is attached defines an O-linked substituent; R³ is hydrogen oroptionally substituted alkyl; R⁴, R⁵ and R⁶ are optionally substitutedalkyl; one R⁷ is an optionally substituted alkyl, an optionallysubstituted arylalkyl, optionally substituted heteroarylalkyl and theother R⁷ is hydrogen or an optionally substituted alkyl; and R^(8A) ishydrogen or optionally substituted alkyl, wherein the wavy lineindicates covalent bonding of D⁺ to the remainder of the LDC structureand wherein each optionally substituted alkyl is independently selected,wherein said glycosidase cleavage results in release of a tubulysincompound (D) from a Ligand Drug Conjugate compound of the composition.

2C. The Ligand Drug Conjugate composition of embodiment 1C wherein thecomposition is represented by the structure of one of Formula 2A-2F:

3C. The Ligand Drug Conjugate composition of embodiment 1C or 2C,wherein the antibody Ligand Unit is capable of selectively binding to anaccessible cell-surface antigen of abnormal cells, wherein the antigenis capable of cellular internalization of bound ADC and ispreferentially present on the abnormal or other unwanted cells incomparison to normal cells.

4C. The Ligand Drug Conjugate composition of embodiment 1C or 2C wherein—O′-Su has the structure of Formula 3:

wherein the wavy line represents covalent bonding of O′ to the remainderof the LDC structure; and R⁴⁵ is —CH₂OH or —CO₂H.

5C. The Ligand Drug Conjugate composition of embodiment 2C wherein thecomposition is represented by the structure of Formula 4:

wherein Ab is the antibody Ligand Unit; J′ is —N(R³³)—, wherein R³³ ishydrogen or methyl; V and Z³ independently are ═CH— or ═N—; R′ ishydrogen or an electron withdrawing group; R⁸ is hydrogen; R⁹ ishydrogen, optionally substituted C₁-C₆ alkyl or optionally substitutedphenyl; R⁴⁵ is —CO₂H; and subscript p is a number ranging from 1 to 24.

6C. The Ligand Drug Conjugate composition of embodiment 5C wherein thecomposition is represented by the structure of Formula 6:

wherein S is a sulfur atom of the antibody Ligand Unit (Ab); theasterisk (*) designates chirality or absence thereof at the indicatedcarbon; A₂₋₄ are independently selected optional subunits of A, wherein—[C(R^(b1))(R^(b1))]_(q)—[HE]- is A₁ when one or more such subunits arepresent; R is hydrogen; R′ is hydrogen or an electron withdrawing group;R^(a1) is hydrogen or a basic unit (BU) wherein BU is a Basic Unithaving the structure of —CH₂—N(R²²)(R²³), or an acid addition saltthereof, wherein R²² and R²³ independently are hydrogen, methyl or ethylor both together with the nitrogen atom to which they are attachedcomprise a 5- or 6-membered heterocycloalkyl, or one of R²², R²³ ishydrogen and the other is an acid labile carbamate protecting group;R^(a2) is hydrogen; subscript q is an integer ranging from 0 to 5 whenHE is present or 1 to 5 when HE is absent; each R^(b1) independently ishydrogen or optionally substituted C₁-C₆ alkyl; HE is absent or is—C(═O)—; R⁴⁵ is —CO₂H; J′ is —NH—; V and Z³ are ═CH₂—; R⁸ is hydrogen;R⁹ is hydrogen or methyl; subscript p is a number ranging from 1 to 16;and wherein the remaining variable groups are as defined for Formula 1Aor Formula 1B.

7C. The Ligand Drug Conjugate composition of embodiment 1C wherein acompound thereof has the structure of Formula 9A or Formula 9B

wherein S is a sulfur atom of the antibody Ligand Unit (Ab); theasterisk (*) designates chirality or absence thereof at the indicatedcarbon; A₂₋₄ are independently selected optional subunits of A, wherein—[C(R^(b1))(R^(b1))]_(q)—[HE]- is A₁ when one or more such subunits arepresent; R is hydrogen; R′ is hydrogen or an electron withdrawing group;R^(a1) is —H or BU wherein BU is a Basic Unit having the structure of—CH₂—N(R²²)(R²³), or an acid addition salt thereof, wherein R²² and R²³independently are hydrogen or methyl or both together with the nitrogenatom to which they are attached define a basic nitrogen-containing 5- or6-membered heterocycloalkyl, or one of R²², R²³ is hydrogen and theother is an acid labile protecting group; R^(a2) is hydrogen; subscriptq is an integer ranging from 0 to 5 when HE is present or from 1 to 5when HE is absent; each R^(b1) independently is hydrogen or optionallysubstituted C₁-C₆ alkyl; HE is absent or is —C(═O)—; J′ is —O— or —NH—;R⁸ and R⁹ are independently —H or optionally substituted alkyl or bothtogether along with the carbon atom to which they are attached define acycloalkyl; and subscript p′ is an integer ranging from 1 to 24; andwherein the remaining variable groups are as defined for Formula 1A orFormula 1B.

8C. The Ligand Drug Conjugate composition of embodiment 7C, wherein acompound thereof has the structure of Formula 10A or Formula 10B

wherein R is hydrogen; R′ is hydrogen, —NO₂, —Cl or —F; HE is —C(═O)—;R⁴⁵ is —CO₂H; J′ is —NH—; V and Z³ are each —CH₂—; R⁸ is hydrogen, R⁹ ishydrogen or methyl; p′ is an integer ranging from 1 to 12; and whereinthe remaining variable groups are as defined for Formula 1A or Formula1B.

9C. The Ligand Drug Conjugate composition, or compound thereof, ofembodiment 6C, 7C or 8C wherein the indicated starred (*) carbon ispredominantly in the same absolute configuration as the alpha carbon ofan L-amino acid when that indicated carbon is chiral.

10C. The Ligand Drug Conjugate composition, or compound thereof, of anyone of embodiments 1C to 5C wherein A and A_(O), when present,independently has the structure of Formula 7 or Formula 8, or any one ofclaims 6 to 9, wherein each of A₂₋₄, when present, independently has thestructure of Formula 7 or Formula 8:

wherein the wavy lines indicated covalent attachment within theConjugate structure, wherein K and L independently are C, N, O or S,provided that when K or L is O or S, R⁴¹ and R⁴² to K or R⁴³ and R⁴⁴ toL are absent, and when K or L am N, one of R⁴¹, R⁴² to K or one of R⁴²,R⁴³ to L are absent, and provided that no two adjacent L areindependently selected as N, O, or S; wherein subscripts e and f areindependently selected integers that range from 0 to 12, and subscript gis an integer ranging from 1 to 12; wherein G is hydrogen, optionallysubstituted C₁-C₆ alkyl, —OH, —OR^(PR), —CO₂H, CO₂R^(PR), wherein R^(PR)is a suitable protecting, —N(R^(PR))(R^(PR)), wherein R^(PR) areindependently a protecting group or R^(PR) together form a suitableprotecting group, or —N(R⁴⁵)(R⁴⁶), wherein one of R⁴⁵, R⁴⁶ is hydrogenor R^(PR), wherein R^(PR) is a suitable protecting group, and the otheris hydrogen or optionally substituted C₁-C₆ alkyl; wherein R³⁸ ishydrogen or optionally substituted C₁-C₆ alkyl; R³⁹—R⁴⁴ independentlyare hydrogen, optionally substituted C₁-C₆ alkyl, optionally substitutedaryl, or optionally substituted heteroaryl, or both R³⁹, R⁴⁰ togetherwith the carbon to which they are attached comprise a C₃-C₆ cycloalkyl,or R⁴¹, R⁴² together with K to which they arm attached when K is C, orR⁴³, R⁴ together with L to which they are attached when L is a carbonatom comprise a C₃-C₆ cycloalkyl, or R⁴⁰ and R⁴¹, or R⁴⁰ and R⁴³, or R⁴¹and R⁴³ to together with the carbon atom or heteroatom to which they areattached and the atoms intervening between those carbon atoms and/orheteroatoms comprise a 5- or 6-membered cycloalkyl or heterocycloalkyl,provided that when K is O or S, R⁴¹ and R⁴² are absent, when K is N, oneof R⁴¹, R⁴² is absent, when L is O or S, R⁴³ and R⁴⁴ are absent, andwhen L is N, one of R⁴³, R⁴⁴ is absent, or wherein A_(O) has a structurecorresponding to an alpha-amino, beta-amino or another amine-containingacid.

11C. The Ligand Drug Conjugate composition, or compound thereof, of anyone of embodiments 1C to 10C wherein the quaternized tubulysin Drug Unit(-D⁺) has the structure of:

wherein subscript m is 0 or 1; Z is an optionally substituted alkyleneor an optionally substituted alkenylene; and R^(7A) is optionallysubstituted aryl or optionally substituted heteroaryl.

12C. The Ligand Drug Conjugate composition, or compound thereof, ofembodiment 11C wherein the quaternized tubulysin Drug Unit (-D⁺) has thestructure of:

wherein R^(7A) is optionally substituted phenyl and R⁸ is hydrogen ormethyl.

13C. The Ligand Drug Conjugate composition, or compound thereof, ofembodiment 12C wherein the quaternized tubulysin Drug Unit (-D⁺) has thestructure of

wherein R⁴ is methyl; subscript u is 0, 1 or 2; R³ is H, methyl, ethyl,propyl, —CH₂—OC(O)R^(3A), —CH₂CH(R^(3B))C(O)R^(3A) or—CH(R^(3B))C(O)NHR^(3A), wherein R^(3A) is C₁-C₆ alkyl and R^(3B) is Hor C₁-C₆ alkyl, independently selected from R^(3A); R^(2A) along withthe oxygen atom to which it is attached is an O-linked substituentselected from the group consisting of —OCH₂OCH₂R^(2B), —OCH₂R^(2B),—OC(O)R^(2B), —CH₂OC(O)R^(2B), —OC(O)N(R^(2B))(R^(2C)), and—OCH₂C(O)N(R^(2B))(R^(2C)), wherein R^(2B) and R^(2C) are independentlyselected from the group consisting of H, C₁-C₆ alkyl and C₂-C₆ alkenyl;and each R^(7B), when present, independently is —OH or —OCH₃.

14C. The Ligand Drug Conjugate composition, or compound thereof, ofembodiment 13C wherein the quaternized tubulysin Drug Unit (-D⁺) has thestructure of

15C. The Ligand Drug Conjugate composition, or compound thereof, of anyone of embodiments 11C to 14C wherein R^(2A) is —CH₂CH₃.

16C. The Ligand Drug Conjugate composition, or compound thereof, of anyone of embodiments 11C to 14C wherein R^(2A) is —CH₂—CH═CH₂.

17C. The Ligand Drug Conjugate composition, or compound thereof, ofembodiment 13C. wherein

R^(2A) is —CH₂CH₃, —CH₂—CH═CH₂ or —CH₂C(CH₃)═CH₂, R^(2B) is —CH₃, R³ is—CH₃ and subscript u is 0, or

R^(2A) is —CH₂CH₃ or —CH₂—CH═CH₂, or —CH₂C(CH₃)═CH₂, R^(2B) is —CH₃, R³is —CH₃ and subscript u is 1, wherein R^(7B) is —OH.

18C. The Ligand Drug Conjugate composition, or compound thereof, ofembodiment 13C wherein the quaternized tubulysin Drug Unit (-D⁺) has thestructure of:

wherein R^(2B) is —CH₃, —CH₂CH₃, —CH₂CH₂CH₃, —CH(CH₃)₂, —CH₂CH(CH₃)₂, or—CH₂C(CH₃)₃.

19C. The Ligand Drug Conjugate composition, or compound thereof, ofembodiment 13C wherein the quaternized tubulysin Drug Unit (-D⁺) has thestructure of:

wherein R^(2B) is hydrogen, methyl or —OCH₃, or —OCH₂R^(2B) is—OCH₂CH═CH₂ or —OCH₂C(CH₃)═CH₂.

20C. The Ligand Drug Conjugate composition, or compound thereof, ofembodiment 13 wherein the quaternized tubulysin Drug Unit (-D⁺) is thatof tubulysin M, which has the structure of:

21C. The Ligand Drug Conjugate composition, or compound thereof, of anyone of embodiments 1C to 20C wherein L_(P) is a aminoalkanedioic acid, adiaminoalkanoic acid, a sulfur-substituted alkanedioic acid, asulfur-substituted aminoalkanoic acid, a diaminoalkanol, anaminoalkanediol, a hydroxyl substituted alkanedioic acid, a hydroxylsubstituted aminoalkanoic acid or a sulfur-substituted aminoalkanolresidue, optionally substituted, wherein the sulfur substituent is inreduced or oxidized form, or L_(P) is an amino acid residue of lysine,arginine, asparagine, glutamine, omithine, citrulline, cysteine,homocysteine, penicillamine, threonine, serine, glutamic acid, asparticacid, tyrosine, histidine or tryptophan, wherein the amino acid is inthe D- or L-configuration.

22C. The Ligand Drug Conjugate composition, or compound thereof, ofembodiment 21C wherein the aminoalkanedioic acid, diaminoalkanoic acid,sulfur-substituted aminoalkanoic acid or hydroxyl substitutedaminoalkanoic acid residue has the structure of Formula A or Formula B:

wherein subscript v is an integer ranging from 1 to 4; subscript v′ isan integer ranging from 0 to 4; X^(LP) is selected from the groupconsisting of —O—, —NR^(LP)—, —S—, —S(═O)—, —S(═O)₂—, —C(═O)—,—C(═O)N(R^(LP))—, —N(R^(LP))C(═O)N(R^(LP))—, and—N(R^(LP))C(═NR^(LP))N(R^(LP))— wherein each R^(LP) is independentlyselected from the group consisting of hydrogen and optionallysubstituted alkyl or two of R^(LP) together along with their interveningatoms define a heterocycloalkyl and any remaining R^(LP) are aspreviously defined; Ar is an arylene or heteroarylene, optionallysubstituted; each R^(E) and R^(F) is independently selected from thegroup consisting of —H, optionally substituted alkyl, optionallysubstituted aryl and optionally substituted heteroaryl, or R^(E) andR^(F) together with the same carbon to which they are attached, or R^(E)and R^(F) from adjacent carbons together with these carbons, defines aoptionally substituted cycloalkyl with any remaining R^(E) and R^(F)substituents as previously defined; and wherein the wavy lines indicatescovalent attachment of the Formula A or Formula B structure within theConjugate structure.

23C. The Ligand Drug Conjugate composition, or compound thereof, of anyone of embodiments 1C to 20C wherein -L_(P)(PEG)- has the structure ofFormula A1 or A2:

wherein X^(LP) is selected from the group consisting of —O—, —NH, —S—and —C(═O)—; R^(E) and R^(F) are independently selected from the groupconsisting of —H, and —C₁-C₄ alkyl; and wherein the wavy line indicatescovalent attachment of Formula A1 or Formula A2 within the Conjugatestructure.

24C. The Ligand Drug Conjugate composition of embodiment 1C wherein thecomposition is represented by the structure of:

wherein Ab is the antibody Ligand Unit; S is a sulfur atom of theantibody Ligand Unit, R^(2A) is saturated C₁-C₄ alkyl, unsaturated C₁-C₄alkyl, —C(═U)R^(2B), wherein R^(2B) is C₁-C₄ alkyl; A_(O) is absent oris an amine-containing acid residue; subscript p is a number rangingfrom 1 to 8; subscript q is an integer ranging from 1 to 4; subscript uis 0 or 1; subscript v is an integer ranging from 1 to 4; R^(7B), whenpresent, is —OH; X^(LP) is selected from the group consisting of —O—,—NH, —S— and —C(═O)—; and R^(E) and R^(F) are independently selectedfrom the group consisting of —H, and C₁-C₄ alkyl.

25C. The Ligand Drug Conjugate composition of embodiment 1C wherein acompound thereof is represented by the structure of:

wherein Ab is the antibody Ligand Unit; S is a sulfur atom of theantibody Ligand Unit; the Ab-S— moiety is bonded to the carbon α or β tothe indicated M³ carboxylic acid; R^(2A) is saturated C₁-C₄ alkyl,unsaturated C₂-C₄ alkyl, —C(═O)R^(2B), wherein R^(2B) is C₁-C₄ alkyl;subscript p′ is an integer ranging from 1 to 8; subscript q is aninteger ranging from 1 to 4; subscript u is 0 or 1; subscript v is aninteger ranging from 1 to 4; R^(7B), when present, is —OH; X^(LP) isselected from the group consisting of —O—, —NH, —S— and —C(═O)—; andR^(E) and R^(F) are independently selected from the group consisting of—H, and C₁-C₄alkyl.

26C. The Ligand Drug Conjugate composition, or compound thereof, ofclaim 24C or 25, wherein R^(2A) is saturated C₁-C₄ alkyl or unsaturatedC₃-C₄ alkyl, wherein saturated C₁-C₄ alkyl is —CH₃, —CH₂CH₃, —CH₂CH₂CH₃and unsaturated C₃-C₄ alkyl is —CH₂CH═CH₂ or —CH(CH₃)CH═CH₂.

27C. The Ligand Drug Conjugate composition, or compound thereof, ofembodiment 24C or 25C wherein R^(2A) is —C(O)CH₃.

28C. The Ligand Drug Conjugate composition, or compound thereof, ofembodiment 24C or 25C wherein R^(2A) is —CH₂CH₃.

29C. The Ligand Drug Conjugate composition, or compound thereof, ofembodiment 24C or 25C wherein R^(2A) is —CH₂CH═CH₂.

30C. The Ligand Drug Conjugate composition, or a compound thereof, ofany one of embodiments 1C to 29C wherein PEG has the structure selectedfrom the group consisting of:

wherein the wavy line indicates site of attachment to X^(LP) of theParallel Connector Unit (L_(P)); R^(PEG1) is an optional PEG AttachmentUnit; R^(PEG2) is a PEG Capping Unit; R^(PEG3) is an PEG Coupling Unit;subscript n ranges from 2 to 72; each subscript n′ is independentlyselected from 1 to 72; and subscript e ranges from 2 to 5.

31C. The Ligand Drug Conjugate composition, or compound thereof, ofembodiment 24C or 25C wherein —X^(LP)-PEG has the structure of:

32C. The Ligand Drug Conjugate composition, or a compound thereof, ofembodiment 31C wherein subscript n is 12 and R^(PEG2) is hydrogen or—CH₃.

33C. The Ligand Drug Conjugate composition of embodiment 1C wherein acompound thereof is represented by the structure of:

wherein Ab is the antibody Ligand Unit; S is a sulfur atom of theantibody Ligand Unit; the Ab-S— moiety is bonded to the carbon α or β tothe indicated M³ carboxylic acid; subscript p′ is an integer rangingfrom 1 to 8; subscript u is 0 or 1; R^(7B), when present, is —OH; andR^(2A) along with the oxygen atom to which it is attached is —OC(O)CH₃,—CH₂CH₃ or —CH₂CH═CH₂.

34C. The Ligand Drug Conjugate composition of embodiment 33C wherein acompound thereof is represented by the structure of:

1D. A Ligand Drug Conjugate composition wherein the composition isrepresented by the structure of Formula 1A

wherein L is an antibody Ligand Unit, thereby defining an Antibody DrugConjugate (ADC); L_(B) is a Ligand Covalent Binding Unit; L_(P) is aParallel Connector Unit; PEG is a Polyethylene Glycol Unit; subscript ais 0 or 1; subscript b is 0 or 1; A is a first optional Stretcher Unitso that subscript a is 0 when A is absent or A is present so thatsubscript a is 1 and is optionally comprised of two, three or fourindependently selected subunits (A₁, A₂, A₃, A₄); B is an Branching Unitor a second optional Stretcher Unit (A_(O)) so that subscript b is 0when B is absent or B is present so that subscript b is 1 and isoptionally comprised of two, three, or four subunits independently of A;subscript n is 1, 2, 3 or 4, provided that subscript b is 1 and B is aBranching when subscript n is 2, 3 or 4 and provided that B is A_(O) oris absent when subscript n is 1; Su is a carbohydrate moiety;—O′-represents an oxygen atom of an O-glycosidic bond cleavable by aglycosidase; -J′-represents a heteroatom, optionally substituted whennitrogen, from a functional group of B, when B is present, or La, when Bis absent; V, Z¹, Z² and Z³ are ═N— or ═C(R²⁴)—, wherein R²⁴ is hydrogenor alkyl, alkenyl or alkynyl, optionally substituted, or halogen, —NO₂,—CN or other electron withdrawing group, or —OCH₃ or other electrondonating group, —O′-Su, or —C(R⁸)(R⁹)-D⁺, wherein at least at least twoof V, Z¹, Z² and Z³ are ═C(R²⁴)—, provided, one any only one R²⁴ is—C(R⁸)(R⁹)-D⁺ so that —C(R⁸)(R⁹)-D⁺ is bonded to one of V, Z¹, Z², Z³when that variable group is ═C(R²⁴)— and one and only one other R²⁴ isso that —O′-Su is bonded to another one of V, Z¹, Z², Z³ when thatvariable group is ═C(R²⁴)—, and the —O′Su and —C(R⁸)(R⁹)-D⁺ substituentsare ortho or para to each other; R⁸ and R⁹ independently are hydrogen,alkyl, alkenyl or alkynyl, optionally substituted, or aryl orheteroaryl, optionally substituted; R′ is hydrogen or is halogen, —NO₂,—CN or other electron withdrawing group; D⁺ is a quaternized tubulysinDrug Unit, preferably having the structure of:

wherein the circle represents an 5-membered nitrogen-heteroarylene andwherein the indicated required substituents to that heteroarylene are ina 1,3-relationship with each other with optional substitution at theremaining positions; subscript m is 0 or 1; R^(2A) is hydrogen oroptionally substituted alkyl, or R^(2A) along with the oxygen atom towhich it is attached defines an O-linked substituent; R³ is hydrogen oroptionally substituted alkyl; R⁴, R⁵ and R⁶ are optionally substitutedalkyl; one R⁷ is an optionally substituted alkyl, an optionallysubstituted arylalkyl, optionally substituted heteroarylalkyl and theother R⁷ is hydrogen or an optionally substituted alkyl; and R^(8A) ishydrogen or optionally substituted alkyl; subscript p is a numberranging from 1 to 24; and wherein the wavy line indicates covalentbonding of D⁺ to the remainder of the Ligand Drug Conjugate structureand wherein each optionally substituted alkyl is independently selected,and wherein said glycosidase cleavage results in release of a tubulysincompound (D) from a Ligand Drug Conjugate compound of the composition,wherein said glycosidase cleavage results in release of a tubulysincompound (D) from a Ligand Drug Conjugate compound of the composition,wherein the Ligand Drug Conjugate compound has the structure of FormulaIA in which subscript p is replaced by subscript p′ wherein subscript p′is an integer ranging from 1 to 24.

2D. The Ligand Drug Conjugate composition of embodiment 1D wherein thecomposition of Formula 1A is represented by the structure of one ofFormula 2A-2F:

3D. The Ligand Drug Conjugate composition of embodiment 1D or 2D,wherein the antibody Ligand Unit is capable of selectively binding to anaccessible cell-surface antigen of abnormal cells, wherein the antigenis capable of cellular internalization of bound ADC and ispreferentially present on the abnormal or other unwanted cells incomparison to normal cells.

4D. The Ligand Drug Conjugate composition of embodiment 1D or 2D wherein—O′-Su has the structure of Formula 3:

wherein the wavy line represents covalent bonding of O′ to the remainderof the LDC structure; and R⁴⁵ is —CH₂OH or —CO₂H.

5D. The Ligand Drug Conjugate composition of embodiment 2D wherein thecomposition is represented by the structure of Formula 4:

wherein Ab is the antibody Ligand Unit; J′ is —N(R³³)—, wherein R³³ ishydrogen or methyl; V and Z³ independently are ═CH— or ═N—; R′ ishydrogen or an electron withdrawing group; R⁸ is hydrogen; R⁹ ishydrogen, optionally substituted C₁-C₆ alkyl or optionally substitutedphenyl; R⁴⁵ is —CO₂H; and subscript p is a number ranging from 1 to 24.

6D. The Ligand Drug Conjugate composition of embodiment 5D wherein thecomposition is represented by the structure of Formula 6:

wherein S is a sulfur atom of the antibody Ligand Unit (Ab); theasterisk (*) designates chirality or absence thereof at the indicatedcarbon; A₂₋₄ are independently selected optional subunits of A, wherein—[C(R^(b1))(R^(b1))]_(q)—[HE]- is A₁ when one or more such subunits arepresent; R is hydrogen; R′ is hydrogen or an electron withdrawing group;R^(a1) is hydrogen or a basic unit (BU) wherein BU is a Basic Unithaving the structure of —CH₂—N(R²²)(R²³), or an acid addition saltthereof, wherein R²² and R²³ independently are hydrogen, methyl or ethylor both together with the nitrogen atom to which they are attachedcomprise a 5- or 6-membered heterocycloalkyl, or one of R²², R²³ ishydrogen and the other is an acid labile carbamate protecting group;R^(a2) is hydrogen; subscript q is an integer ranging from 0 to 5 whenHE is present or 1 to 5 when HE is absent; each R^(b1) independently ishydrogen or optionally substituted C₁-C₆ alkyl; HE is absent or is—C(═O)—; R⁴⁵ is —CO₂H; J′ is —NH—; V and Z³ are ═CH₂—; R⁸ is hydrogen;R⁹ is hydrogen or methyl; subscript p is a number ranging from 1 to 16;and wherein the remaining variable groups are as defined for Formula 1A.

7D. The Ligand Drug Conjugate composition of embodiment 1D wherein acompound thereof has the structure of Formula 9A or Formula 9B

wherein S is a sulfur atom of the antibody Ligand Unit (Ab); theasterisk (*) designates chirality or absence thereof at the indicatedcarbon; A₂₋₄ are independently selected optional subunits of A, wherein—[C(R^(b1))(R^(b1))]_(q)—[HE]- is A₁ when one or more such subunits arepresent; R is hydrogen; R′ is hydrogen or an electron withdrawing group;R^(a) is —H or BU wherein BU is a Basic Unit having the structure of—CH₂—N(R²²)(R²³), or an acid addition salt thereof, wherein R²² and R²³independently are hydrogen or methyl or both together with the nitrogenatom to which they are attached define a basic nitrogen-containing 5- or6-membered heterocycloalkyl, or one of R²², R²³ is hydrogen and theother is an acid labile protecting group; R^(a2) is hydrogen; subscriptq is an integer ranging from 0 to 5 when HE is present or from 1 to 5when HE is absent; each R^(b1) independently is hydrogen or optionallysubstituted C₁-C₆ alkyl; HE is absent or is —C(═O)—; J′ is —O— or —NH—;R⁸ and R⁹ are independently —H or optionally substituted alkyl, or bothtogether along with the carbon atom to which they are attached define acycloalkyl; and subscript p′ is an integer ranging from 1 to 24; andwherein the remaining variable groups are as defined for Formula 1A.

8D. The Ligand Drug Conjugate composition of embodiment 7D, wherein acompound thereof has the structure of Formula 10A or Formula 10B:

wherein R is hydrogen; R′ is hydrogen, —NO₂, —Cl or —F; HE is —C(═O)—;R⁴⁵ is —CO₂H; J′ is —NH—; V and Z³ are each ═CH₂—; R⁸ is hydrogen; R⁹ ishydrogen or methyl; p′ is an integer ranging from 1 to 12; and whereinthe remaining variable groups are as defined for Formula IA.

9D. The Ligand Drug Conjugate composition, or compound thereof, ofembodiment 6D, 7D or 8D wherein the indicated starred (*) carbon ispredominantly in the same absolute configuration as the alpha carbon ofan L-amino acid when that indicated carbon is chiral.

10D. The Ligand Drug Conjugate composition, or compound thereof, of anyone of embodiments 1D to 5D wherein A and A_(O), when present,independently has the structure of Formula 7 or Formula 8, or any one ofembodiments 6D to 9D, wherein each of A₂₋₄, when present, independentlyhas the structure of Formula 7 or Formula 8:

wherein the wavy lines indicated covalent attachment within theConjugate structure, wherein K and L independently are C, N, O or S,provided that when K or L is O or S, R⁴¹ and R⁴² to K or R⁴³ and R⁴⁴ toL are absent, and when K or L am N, one of R⁴¹, R⁴² to K or one of R⁴²,R⁴³ to L are absent, and provided that no two adjacent L areindependently selected as N, O, or S; wherein subscripts e and f areindependently selected integers that range from 0 to 12, and subscript gis an integer ranging from 1 to 12; wherein G is hydrogen, optionallysubstituted C₁-C₆ alkyl, —OH, —OR^(PR), —CO₂H, CO₂R^(PR), wherein R^(PR)is a suitable protecting, —N(R^(PR))(R^(PR)), wherein R^(PR) areindependently a protecting group or R^(PR) together form a suitableprotecting group, or —N(R⁴⁵)(R⁴⁶), wherein one of R⁴⁵, R⁴⁶ is hydrogenor R^(PR), wherein R^(PR) is a suitable protecting group, and the otheris hydrogen or optionally substituted C₁-C₆ alkyl; wherein R³⁸ ishydrogen or optionally substituted C₁-C₆ alkyl; R³⁹—R⁴⁴ independentlyare hydrogen, optionally substituted C₁-C₆ alkyl, optionally substitutedaryl, or optionally substituted heteroaryl, or both R³⁹, R⁴⁰ togetherwith the carbon to which they are attached comprise a C₃-C₆ cycloalkyl,or R⁴¹, R⁴² together with K to which they arm attached when K is C, orR⁴³, R⁴⁴ together with L to which they are attached when L is a carbonatom comprise a C₃-C₆ cycloalkyl, or R⁴⁰ and R⁴¹, or R⁴⁰ and R⁴³, or R⁴¹and R⁴³ to together with the carbon atom or heteroatom to which they areattached and the atoms intervening between those carbon atoms and/orheteroatoms comprise a 5- or 6-membered cycloalkyl or heterocycloalkyl,provided that when K is O or S. R⁴¹ and R⁴² are absent, when K is N, oneof R⁴¹, R⁴² is absent, when L is O or S, R⁴³ and R⁴⁴ are absent, andwhen L is N, one of R⁴³, R⁴⁴ is absent, or wherein A_(O) has a structurecorresponding to an alpha-amino, beta-amino or another amine-containingacid.

11D. The Ligand Drug Conjugate composition, or compound thereof, of anyone of embodiments 1D to 10D wherein the quaternized tubulysin Drug Unit(-D⁺) has the structure of

wherein subscript m is 0 or 1; Z is an optionally substituted alkyleneor an optionally substituted alkenylene; and R^(7A) is optionallysubstituted aryl or optionally substituted heteroaryl.

12D. The Ligand Drug Conjugate composition, or compound thereof, ofembodiment 11D wherein the quaternized tubulysin Drug Unit (-D⁺) has thestructure of

wherein R^(7A) is optionally substituted phenyl and R⁸ is hydrogen ormethyl.

13D. The Ligand Drug Conjugate composition, or compound thereof, ofembodiment 12D wherein the quaternized tubulysin Drug Unit (-D⁺) has thestructure of:

wherein R⁴ is methyl; subscript u is 0, 1 or 2; R³ is H, methyl, ethyl,propyl, —CH₂—OC(O)R^(3A), —CH₂CH(R^(3B))C(O)R^(3A) or—CH(R^(3B))C(O)NHR^(3A), wherein R^(3A) is C₁-C₆ alkyl and R^(3B) is Hor C₁-C₆ alkyl, independently selected from R^(3A); R^(2A) along withthe oxygen atom to which it is attached is an O-linked substituentselected from the group consisting of —OCH₂OCH₂R^(2B), —OCH₂R^(2B),—OC(O)R_(2B), —CH₂OC(O)R^(2B), —OC(O)N(R^(2B))(R^(2C)), and—OCH₂C(O)N(R^(2B))(R^(2C)), wherein R^(2B) and R^(2C) are independentlyselected from the group consisting of H, C₁-C₆ alkyl and C₂-C₆ alkenyl;and each R^(7B), when present, independently is —OH or —OCH₃.

14D. The Ligand Drug Conjugate composition, or compound thereof, ofembodiment 13D wherein the quaternized tubulysin Drug Unit (-D⁺) has thestructure of:

15D. The Ligand Drug Conjugate composition, or compound thereof, of anyone of embodiments 11D to 14D wherein R^(2A) is —CH₂CH₃.

16D. The Ligand Drug Conjugate composition, or compound thereof, of anyone of embodiments 11 to 14 wherein R^(2A) is —CH₂—CH═CH₂.

17D. The Ligand Drug Conjugate composition, or compound thereof, ofembodiment 13D, wherein R^(2A) is —CH₂CH₃, —CH₂—CH═CH₂ or—CH₂C(CH₃)═CH₂, R^(2B) is —CH₃, R³ is —CH₃ and subscript u is 0, orR^(2A) is —CH₂CH₃ or —CH₂—CH═CH₂, or —CH₂C(CH₃)═CH₂, R^(2B) is —CH₃, R³is —CH₃ and subscript u is 1, wherein R^(7B) is —OH.

18D. The Ligand Drug Conjugate composition, or compound thereof, ofembodiment 13D wherein the quaternized tubulysin Drug Unit (-D⁺) has thestructure of

wherein R^(2B) is —CH₃, —CH₂CH₃, —CH₂CH₂CH₃, —CH(CH₃)₂, —CH₂CH(CH₃)₂, or—CH₂C(CH₃)₃.

19D. The Ligand Drug Conjugate composition, or compound thereof, ofembodiment 13D wherein the quaternized tubulysin Drug Unit (-D⁺) has thestructure of

wherein R^(2B) is hydrogen, methyl or —OCH₃, or —OCH₂R^(2B) is—OCH₂CH═CH₂ or —OCH₂C(CH₃)═CH₂.

20D. The Ligand Drug Conjugate composition, or compound thereof, ofembodiment 13D wherein the quaternized tubulysin Drug Unit -D⁺ is thatof tubulysin M, which has the structure of:

21D. The Ligand Drug Conjugate composition, or compound thereof, of anyone of embodiments 1D to 20D wherein L_(P) is a aminoalkanedioic acid, adiaminoalkanoic acid, a sulfur-substituted alkanedioic acid, asulfur-substituted aminoalkanoic acid, a diaminoalkanol, anaminoalkanediol, a hydroxyl substituted alkanedioic acid, a hydroxylsubstituted aminoalkanoic acid or a sulfur-substituted aminoalkanolresidue, optionally substituted, wherein the sulfur substituent is inreduced or oxidized form, or L_(P) is an amino acid residue of lysine,arginine, asparagine, glutamine, omithine, citrulline, cysteine,homocysteine, penicillamine, threonine, serine, glutamic acid, asparticacid, tyrosine, histidine or tryptophan, wherein the amino acid is inthe D- or L-configuration.

22D. The Ligand Drug Conjugate composition, or compound thereof, ofembodiment 21D wherein the aminoalkanedioic acid, diaminoalkanoic acid,sulfur-substituted aminoalkanoic acid or hydroxyl substitutedaminoalkanoic acid residue has the structure of Formula A or Formula B:

wherein subscript v is an integer ranging from 1 to 4; subscript v′ isan integer ranging from 0 to 4; X^(LP) is selected from the groupconsisting of —O—, —NR^(LP)—, —S—, —S(═O)—, —S(═O)₂—, —C(═O)—,—C(═O)N(R^(LP))—, —N(R^(LP))C(═O)N(R^(LP))—, and—N(R^(LP))C(═NR^(LP))N(R^(LP))— wherein each R^(LP) is independentlyselected from the group consisting of hydrogen and optionallysubstituted alkyl or two of R^(LP) together along with their interveningatoms define a heterocycloalkyl and any remaining R^(LP) are aspreviously defined; Ar is an arylene or heteroarylene, optionallysubstituted; each R^(E) and R^(F) is independently selected from thegroup consisting of —H, optionally substituted alkyl, optionallysubstituted aryl and optionally substituted heteroaryl, or R^(E) andR^(F) together with the same carbon to which they are attached, or R^(E)and R^(F) from adjacent carbons together with these carbons, defines aoptionally substituted cycloalkyl with any remaining R^(E) and R^(F)substituents as previously defined; and wherein the wavy lines indicatescovalent attachment of the Formula A or Formula B structure within theConjugate structure.

23D. The Ligand Drug Conjugate composition, or compound thereof, of anyone of embodiments 1D to 20D wherein -L_(P)(PEG)- has the structure ofFormula A1 or A2:

wherein X^(LP) is selected from the group consisting of —O—, —NH, —S—and —C(═O)—; R^(E) and R^(F) are independently selected from the groupconsisting of —H, and —C₁-C₄ alkyl; and wherein the wavy line indicatescovalent attachment of Formula A1 or Formula A2 within the Conjugatestructure.

24D. The Ligand Drug Conjugate composition of embodiment 1D wherein thecomposition is represented by the structure of:

wherein Ab is the antibody Ligand Unit; S is a sulfur atom of theantibody Ligand Unit, R^(2A) is saturated C₁-C₄ alkyl, unsaturated C₁-C₄alkyl, —C(═U)R^(2B), wherein R^(2B) is C₁-C₄ alkyl; A_(O) is absent oris an amine-containing acid residue; subscript p is a number rangingfrom 1 to 8; subscript q is an integer ranging from 1 to 4; subscript uis 0 or 1; subscript v is an integer ranging from 1 to 4; R^(7B), whenpresent, is —OH; X^(LP) is selected from the group consisting of —O—,—NH, —S— and —C(═O)—; and R^(E) and R^(F) are independently selectedfrom the group consisting of —H, and C₁-C₄ alkyl.

25D. The Ligand Drug Conjugate composition of embodiment 1D wherein acompound thereof is represented by the structure of:

wherein Ab is the antibody Ligand Unit; S is a sulfur atom of theantibody Ligand Unit; the Ab-S— moiety is bonded to the carbon α or β tothe indicated M³ carboxylic acid; R^(2A) is saturated C₁-C₄ alkyl,unsaturated C₂-C₄ alkyl, —C(═O)R^(2B), wherein R^(2A) is C₁-C₄ alkyl;subscript p′ is an integer ranging from 1 to 8; subscript q is aninteger ranging from 1 to 4; subscript u is 0 or 1; subscript v is aninteger ranging from 1 to 4; R^(7B), when present, is —OH; X^(LP) isselected from the group consisting of —O—, —NH, —S— and —C(═O)—; andR^(E) and R^(F) are independently selected from the group consisting of—H, and C₁-C₄alkyl.

26D. The Ligand Drug Conjugate composition, or compound thereof, ofembodiment 24D or 25D, wherein R^(2A) is saturated C₁-C₄ alkyl orunsaturated C₃-C₄ alkyl, wherein saturated C₁-C₄ alkyl is —CH₃, —CH₂CH₃,—CH₂CH₂CH₃ and unsaturated C₃-C₄ alkyl is —CH₂CH═CH₂ or —CH(CH₃)CH═CH₂.

27D. The Ligand Drug Conjugate composition, or compound thereof, ofembodiment 24D or 25D wherein R^(2A) is —C(O)CH₃.

28D. The Ligand Drug Conjugate composition, or compound thereof, ofembodiment 24D or 25D wherein R^(2A) is —CH₂CH₃.

29D. The Ligand Drug Conjugate composition, or compound thereof, ofembodiment 24D or 25D wherein R^(2A) is —CH₂CH═CH₂.

30D. The Ligand Drug Conjugate composition, or a compound thereof, ofany one of embodiments 1D to 29D wherein PEG has the structure selectedfrom the group consisting of:

wherein the wavy line indicates site of attachment to X^(LP) of theParallel Connector Unit (L_(P)); R^(PEG1) is an optional PEG AttachmentUnit; R^(PEG2) is a PEG Capping Unit; R^(PEG3) is an PEG Coupling Unit;subscript n ranges from 2 to 72; each subscript n′ is independentlyselected from 1 to 72; and subscript e ranges from 2 to 5.

31D. The Ligand Drug Conjugate composition, or compound thereof, ofembodiment 24D or 25D wherein —X^(LP)-PEG has the structure of:

32D. The Ligand Drug Conjugate composition, or a compound thereof, ofembodiment 31D wherein subscript n is 12 and R^(PEG2) is hydrogen or—CH₃.

33D. The Ligand Drug Conjugate composition of embodiment 1D wherein acompound thereof is represented by the structure of:

wherein Ab is the antibody Ligand Unit; S is a sulfur atom of theantibody Ligand Unit; the Ab-S— moiety is bonded to the carbon α or β tothe indicated M³ carboxylic acid; subscript p′ is an integer rangingfrom 1 to 8; subscript u is 0 or 1; R^(7B), when present, is —OH; andR^(2A) along with the oxygen atom to which it is attached is —OC(O)CH₃,—CH₂CH₃ or —CH₂CH═CH₂.

34D. The Ligand Drug Conjugate composition of embodiment 33D wherein acompound thereof is represented by the structure of:

35D. A Drug Linker compound, wherein the compound has the structure ofFormula IA:

wherein L_(B)′ is a Ligand Covalent Binding Unit precursor; L_(P) is aParallel Connector Unit; PEG is a Polyethylene Glycol Unit; subscript ais 0 or 1; subscript b is 0 or 1; A is a first optional Stretcher Unitso that subscript a is 0 when A is absent or A is present so thatsubscript a is 1 and is optionally comprised of two, three or fourindependently selected subunits (A₁, A₂, A₃, A₄); B is an Branching Unitor a second optional Stretcher Unit (A_(O)) so that subscript b is 0when B is absent or B is present so that subscript b is 1 and isoptionally comprised of two, three or four subunits independently of A;subscript n is 1, 2, 3 or 4, provided that subscript b is 1 and B is aBranching when subscript n is 2, 3 or 4 and provided that B is A_(O) oris absent when subscript n is 1; Su is a carbohydrate moiety: —O′—represents an oxygen atom of an O-glycosidic bond cleavable by aglycosidase; -J′- represents a heteroatom, optionally substituted whennitrogen, from a functional group bonding B, when B is present, orL_(B), when B is absent to the remainder of the LDC; V, Z¹, Z² and Z³are ═N— or ═C(R²⁴)—, wherein R²⁴ is hydrogen or alkyl, alkenyl oralkynyl, optionally substituted, or halogen, —NO₂, —CN or other electronwithdrawing group, an electron donating group, —O′-Su, or —C(R⁸)(R⁹)-D⁺,wherein at least at least two of V, Z¹, Z² and Z³ are ═C(R²⁴)—,provided, one any only one R⁴ is —C(R⁸)(R⁹)-D⁺ so that —C(R⁸)(R⁹)-D⁺ isbonded to one of V, Z¹, Z², Z³ when that variable group is ═C(R²⁴)— andone and only one other R⁷⁴ is so that —O′-Su is bonded to another one ofV, Z¹, Z², Z when that variable group is ═C(R²⁴)—, and the —O′Su and—C(R⁸)(R⁹)-D⁺ substituents are ortho or para to each other; R⁸ and R⁹independently are hydrogen, alkyl, alkenyl or alkynyl, optionallysubstituted, or aryl or heteroaryl, optionally substituted; R′ ishydrogen or is halogen, —NO₂, —CN or other electron withdrawing group;D⁺ is a quaternized tubulysin Drug Unit preferentially having thestructure of:

wherein the circle represents an 5-membered nitrogen-heteroarylene andwherein the indicated required substituents to that heteroarylene are ina 1,3-relationship with each other with optional substitution at theremaining positions; subscript m is 0 or 1; R^(2A) is hydrogen oroptionally substituted alkyl or R^(2A) along with the oxygen atom towhich it is attached defines an O-linked substituent other than —OH; R³is hydrogen or optionally substituted alkyl; R⁴, R⁵ and R⁶ areoptionally substituted alkyl; one R⁷ is an optionally substituted alkyl,an optionally substituted arylalkyl, optionally substitutedheteroarylalkyl and the other R⁷ is hydrogen or an optionallysubstituted alkyl; and R^(8A) is hydrogen or optionally substitutedalkyl, wherein the wavy line indicates covalent bonding of D⁺ to theremainder of the Drug Linker structure and wherein optionallysubstituted alkyl are independently selected; and wherein saidglycosidase cleavage results in release of tubulysin compound (D) from aLigand Drug Conjugate compound prepared from the Linker Drug compoundwherein said glycosidase cleavage results in release of a tubulysincompound (D) from a Ligand Drug Conjugate compound of the composition,wherein the Ligand Drug Conjugate compound has the Formula IA structureof embodiment ID in which subscript p is replaced by subscript p′,wherein subscript p′ is an integer ranging from 1 to 24.

36D. The Drug-Linker compound of embodiment 35D wherein L_(B)′- has astructure selected from the group consisting of:

wherein R is hydrogen or C₁-C₆ optionally substituted alkyl; R″ ishydrogen or halogen or R and R′ are independently selected halogen; T is—Cl, —Br, —I, —O-mesyl or —O— tosyl or other sulfonate leaving group; Uis —F, —Cl, —Br, —I, —O—N-succinimide, —O-(4-nitrophenyl),—O-pentafluorophenyl, —O-tetrafluorophenyl or —O—C(═O)—OR⁵⁷; and X² isC₁₋₁₀ alkylene. C₃-C₈-carbocycle, —O—(C₁-C₆ alkyl), -arylene-, C₁-C₁₀alkylene-arylene, -arylene-C₁-C₁₀ alkylene, —C₁-C₁₀alkylene-(C₃-C₆-carbocycle)-, —(C₃-C₈ carbocycle)-C₁-C₁₀ alkylene-,C₁-C₈-heterocycle, —C₁-C₁₀ alkylene-(C₃-C₈ heterocyclo)-,—C₃-C₈-heterocyclo)-C₁-C₁₀ alkylene, —(CH₂CH₂O)_(u), or—CH₂CH₂O)_(u)—CH₂—, wherein subscript u is an integer ranging from 1 to10 and R⁵⁷ is C₁-C₆ alkyl or aryl.

37D. The Drug-Linker compound of embodiment 35D wherein the compound hasthe structure of one of Formula IIA-IIF:

38D. The Drug-Linker compound of any one of embodiments 35D to 37Dwherein —O′-Su has the structure of Formula 3:

wherein the wavy line represents covalent bonding of O′ to the remainderof the Drug Linker compound structure; and R⁴⁵ is —CH₂OH or —CO₂H.

39D. The Drug-Linker compound of embodiment 35D wherein the compound hasthe structure of Formula IV:

wherein J′ is —N(R³³)—, wherein R³³ is hydrogen or methyl; V and Z³independently are ═CH— or ═N—; R′ is hydrogen or an electron withdrawinggroup; R⁸ is hydrogen; R⁹ is hydrogen, optionally substituted C₁-C₆alkyl or optionally substituted phenyl; and R⁴⁵ is —CO₂H.

40D. The Drug-Linker compound of embodiment 35 wherein subscript a is 1;and L_(B)′-A- of Formula IA has the structure of Formula V:

wherein the —[C(R^(b1))(R^(b1))]_(q)—[HE]- moiety is A or A₁, wherein A₁is a subunit of A; A₂₋₄ are optional subunits of A; R is hydrogen,chloro or C₁-C₄ alkyl; R″ is hydrogen or chloro; R^(a1) is hydrogen,optionally substituted alkyl or a Basic Unit (BU), optionally protected;and R^(a2) is hydrogen or optionally substituted alkyl, or R^(a1) andR^(a2) together with the carbon atom to which they are attached definesa nitrogen-containing heterocycloalkyl; HE is an optional HydrolysisEnhancer (HE) Unit; subscript q is an integer ranging from 0 to 6; eachR^(b1) independently is hydrogen, optionally substituted C₁-C₆ alkyl,optionally substituted aryl or optionally substituted heteroaryl, or twoR^(b1) together with the carbon(s) to which they are attached comprise aC₃-C₆ cycloalkyl or one R^(b1) and HE together with the carbon to whichthey are attached define a 5 or 6-membered cycloalkyl or a 5- or6-membered heterocycloalkyl and the other R^(b1) is hydrogen, optionallysubstituted C₁-C₆ alkyl, optionally substituted aryl or optionallysubstituted heteroaryl; BU, optionally protected, has the structure of—[C(R¹)(R¹)]—[C(R²)(R²)]_(r)—N(R²²)(R²³), or an acid addition saltthereof, wherein subscript r is 0, 1, 2 or 3; each R¹ independently ishydrogen or lower alkyl or two R¹ together with the carbon to which theyare attached comprise a C₃-C₆ cycloalkyl, and each R² independently ishydrogen, optionally substituted C₁-C₆ alkyl, optionally substitutedaryl or optionally substituted heteroaryl, or two R² together with thecarbon(s) to which they are attached and any intervening carbons definea C₃-C₆ cycloalkyl, or one R¹ and one R² together with the carbons towhich they are attached and any intervening carbons define a 5- or6-membered cycloalkyl and the remaining R¹ and R² are as defined; andR²² and R²³ independently, hydrogen, optionally substituted C₁-C₆ alkyl,or an acid-labile protecting group, or together with the nitrogen towhich they are attached define a 5- or 6-membered heterocycloalkyl, oneof R²², R²³ is hydrogen and the other is an acid labile protectinggroup; and wherein the wavy line indicates the site of covalentattachment to the remainder of the Drug Linker compound structure.

41D. The Drug Linker compound of embodiment 40D wherein Formula V hasthe structure of Formula VA:

wherein subscript q is an integer ranging from 0 to 4.

42D. The Drug Linker compound of embodiment 40D wherein Formula V hasthe structure of Formula VB:

wherein one of R²², R²³ is hydrogen and the other is an acid labilecarbamate protecting group; and subscript q is an integer ranging from 0to 4.

43D. The Drug Linker compound of embodiment 41D or 42D wherein FormulaVA or Formula VB respectively has the structure of:

44D. The Drug Linker compound of embodiment 40D wherein the compound hasthe structure of Formula VI

wherein the asterisk (*) designates chirality or absence thereof at theindicated carbon; A₂₋₄ are independently selected optional subunits ofA, wherein —[C(R^(b1))(R^(b1))]_(q)—[HE]- is A₁ when one or more suchsubunits are present; one of R and R″ is hydrogen and the other ishydrogen or chloro; R′ is hydrogen or an electron withdrawing group;R^(a1) is hydrogen or a basic unit (BU), optionally protected, havingthe structure of —CH₂—N(R²²)(R²³), or an acid addition salt thereof,wherein R²² and R²³ independently are hydrogen, methyl or ethyl or bothtogether with the nitrogen atom to which they are attached comprise a 5-or 6-membered heterocycloalkyl, or one of R²², R²³ is hydrogen and theother is an acid labile carbamate protecting group; R^(a2) is hydrogen;subscript q is an integer ranging from 0 to 5 when HE is present or 1 to5 when HE is absent; each R^(b1) independently is hydrogen or optionallysubstituted C₁-C₆ alkyl; HE is absent or is —C(═O)—; R⁴⁵ is —CO₂H; J′ is—NH—; V and Z³ are ═CH₂—; R⁸ is hydrogen; and R⁹ is hydrogen or methyl.

45D. The Drug Linker compound of embodiment 44D wherein the indicatedstarred (*) carbon is predominantly in the same absolute configurationas the alpha carbon of an L-amino acid when that indicated carbon ischiral.

46D. The Drug Linker compound of any one of embodiments 35D to 39Dwherein A and A_(O), when present, independently has the structure ofFormula 7 or Formula 8, or any one of claims 40 to 45, wherein each ofA₂₋₄, when present, independently has the structure of Formula 7 orFormula 8:

wherein the wavy lines indicated covalent attachment within the DrugLinker compound structure and wherein K and L independently are C, N, Oor S, provided that when K or L is O or S, R⁴¹ and R⁴² to K or R⁴³ andR⁴⁴ to L are absent, and when K or L are N, one of R⁴¹, R⁴² to K or oneof R⁴², R⁴³ to L are absent, and provided that no two adjacent L areindependently selected as N, O, or S; wherein subscripts e and f areindependently selected integers that range from 0 to 12, and subscript gis an integer ranging from 1 to 12; wherein G is hydrogen, optionallysubstituted C₁-C₆ alkyl, —OH, -OR^(PR), —CO₂H, CO₂R^(PR), wherein R^(PR)is a suitable protecting, —N(R^(PR))(R^(PR)), wherein R^(PR) areindependently a protecting group or R^(PR) together form a suitableprotecting group, or —N(R⁴⁵)(R⁴⁶), wherein one of R⁴⁵, R⁴⁶ is hydrogenor R^(PR), wherein R^(PR) is a suitable protecting group, and the otheris hydrogen or optionally substituted C₁-C₆ alkyl; wherein R³⁸ ishydrogen or optionally substituted C₁-C₆ alkyl; R³⁹—R⁴⁴ independentlyare hydrogen, optionally substituted C₁-C₆ alkyl, optionally substitutedaryl, or optionally substituted heteroaryl, or both R³⁹, R⁴⁰ togetherwith the carbon to which they are attached comprise a C₃-C₆ cycloalkyl,or R⁴¹, R⁴² together with K to which they are attached when K is C, orR⁴³, R⁴⁴ together with L to which they are attached when L is a carbonatom comprise a C₁-C₆ cycloalkyl, or R⁴⁰ and R⁴¹, or R⁴⁰ and R⁴³, or R⁴¹and R⁴³ to together with the carbon atom or heteroatom to which they areattached and the atoms intervening between those carbon atoms and/orheteroatoms comprise a 5- or 6-membered cycloalkyl or heterocycloalkyl,provided that when K is O or S. R⁴¹ and R⁴² are absent, when K is N, oneof R⁴¹, R⁴² is absent, when L is O or S, R⁴³ and R⁴⁴ are absent, andwhen L is N, one of R⁴³, R⁴⁴ is absent, or wherein A_(O) has a structurecorresponding to an alpha-amino, beta-amino or another amine-containingacid.

47D. The Drug Linker compound of any one of embodiments 35D to 46Dwherein the quaternized tubulysin Drug Unit (-D⁺) has the structure of:

wherein subscript m is 0 or 1; Z is an optionally substituted alkyleneor an optionally substituted alkenylene; and R^(7A) is optionallysubstituted aryl or optionally substituted heteroaryl.

48D. The Drug Linker compound of embodiment 47D wherein the quaternizedtubulysin Drug Unit (-D⁺) has the structure of:

wherein R^(7A) is optionally substituted phenyl and R⁸ is hydrogen ormethyl.

49D. The Drug Linker compound of embodiment 50D wherein the quaternizedtubulysin Drug Unit (-D⁺) has the structure of

wherein R⁴ is methyl; subscript u is 0, 1 or 2; R³ is H, methyl, ethyl,propyl, —CH₂—OC(O)R^(3A), —CH₂CH(R^(3B))C(O)R^(3A) or—CH(R^(3B))C(O)NHR^(3A), wherein R^(3A) is C₁-C₆ alkyl and R^(3B) is Hor C₁-C₆ alkyl, independently selected from R^(3A); R^(2A) along withthe oxygen atom to which it is attached is an O-linked substituentselected from the group consisting of —OCH₂OCH₂R^(2B), —OCH₂R^(2B),—OC(O)R^(2B), —CH₂OC(O)R^(2B), —OC(O)N(R^(2A))(R^(2C)), and—OCH₂C(O)N(R^(2B))(R^(2C)), wherein R^(2B) and R^(2C) are independentlyselected from the group consisting of H, C₁-C₆ alkyl and C₂-C₆ alkenyl;and each R^(7B), when present, independently is —OH or —OCH₃.

50D. The Drug Linker compound of embodiment 49D wherein the quaternizedtubulysin Drug Unit (-D⁺) has the structure of

51D. The Drug Linker compound of any one of embodiments 47D to 50Dwherein R^(2A) is —CH₂CH₃.

52D. The Drug Linker compound of any one of embodiments 47D to 50Dwherein R^(2A) is —CH₂—CH═CH₂.

53D. The Drug Linker compound of embodiment 49D, wherein R^(2A) is—CH₂CH₃, —CH₂—CH═CH₂ or —CH₂C(CH₃)═CH₂, R^(2B) is —CH₃, R³ is —CH₃ andsubscript u is 0, or R^(2A) is —CH₂CH₃ or —CH₂—CH═CH₂, or—CH₂C(CH₃)═CH₂, R^(2B) is —CH₃, R³ is —CH₃ and subscript u is 1, whereinR^(7B) is —OH.

54D. The Drug Linker compound of embodiment 49D wherein the quaternizedtubulysin Drug Unit (-D⁺) has the structure of:

wherein R^(2B) is —CH₃, —CH₂CH₃, —CH₂CH₂CH₃, —CH(CH₃)₂, —CH₂CH(CH₃)₂, or—CH₂C(CH₃)₃.

55D. Drug Linker compound of embodiment 49D, wherein the quaternizedtubulysin Drug Unit (-D⁺) has the structure of:

wherein R^(2B) is hydrogen, methyl or —OCH₃, or —OCH₂R^(2B) is—OCH₂CH═CH₂ or —OCH₂C(CH₃)═CH₂.

56D. The Drug Linker compound of embodiment 49D, wherein the quaternizedtubulysin Drug Unit -D⁺ is that of tubulysin M, which has the structureof:

57D. The Drug Linker compound of any one of embodiments 35D to 56Dwherein Le is a aminoalkanedioic acid, a diaminoalkanoic acid, asulfur-substituted alkanedioic acid, a sulfur-substituted aminoalkanoicacid, a diaminoalkanol, an aminoalkanediol, a hydroxyl substitutedalkanedioic acid, a hydroxyl substituted aminoalkanoic acid or asulfur-substituted aminoalkanol residue, optionally substituted, whereinthe sulfur substituent is in reduced or oxidized form, or L_(P) is anamino acid residue of lysine, arginine, asparagine, glutamine,ornithine, citrulline, cysteine, homocysteine, penicillamine, threonine,serine, glutamic acid, aspartic acid, tyrosine, histidine or tryptophan,wherein the amino acid is in the D- or L-configuration.

58D. The Drug Linker compound of embodiment 57D wherein theaminoalkanedioic acid, diaminoalkanoic acid, sulfur-substitutedaminoalkanoic acid or hydroxyl substituted aminoalkanoic acid residuehas the structure of Formula A or Formula B:

wherein subscript v is an integer ranging from 1 to 4; subscript v′ isan integer ranging from 0 to 4; X^(LP) is selected from the groupconsisting of —O—, —NR^(LP)—, —S—, —S(═O)—, —S(═O)₂—, —C(═O)—,—C(═O)N(R^(LP))—, —N(R^(LP))C(═O)N(R^(LP))—, and—N(R^(LP))C(═NR^(LP))N(R^(LP))— wherein each R^(LP) is independentlyselected from the group consisting of hydrogen and optionallysubstituted alkyl or two of R^(LP) together along with their interveningatoms define a heterocycloalkyl and any remaining R^(LP) are aspreviously defined; Ar is an arylene or heteroarylene, optionallysubstituted; each R^(E) and R^(F) is independently selected from thegroup consisting of —H, optionally substituted alkyl, optionallysubstituted aryl and optionally substituted heteroaryl, or R^(E) andR^(F) together with the same carbon to which they are attached, or R^(E)and R^(F) from adjacent carbons together with these carbons, defines aoptionally substituted cycloalkyl with any remaining R^(E) and R^(F)substituents as previously defined; and wherein the wavy lines indicatescovalent attachment of the Formula A or Formula B structure within theDrug Linker compound structure.

59D. The Drug Linker compound of any one of embodiment 35D to 56Dwherein -L_(P)(PEG)- has the structure of Formula A1 or A2:

wherein X^(LP) is selected from the group consisting of —O—, —NH, —S—and —C(═O)—; R^(E) and R^(F) are independently selected from the groupconsisting of —H, and —C₁-C₄ alkyl; and wherein the wavy line indicatescovalent attachment of Formula A1 or Formula A2 within the Drug Linkercompound structure.

60D. The Drug Linker compound of embodiment 35D wherein the compound isrepresented by the structure of

wherein R^(2A) is saturate C₁-C₄alkyl, unsaturated C₂-C₄ alkyl—C(═O)R^(2B), wherein R^(2B) is C₁-C₄ alkyl; A_(O) is absent or is anamine-containing acid residue; subscript q is an integer ranging from 1to 4; subscript u is 0 or 1; subscript v is an integer ranging from 1 to4; R^(7B), when present, is —OH; X^(LP) is selected from the groupconsisting of —O—, —NH, —S— and —C(═O)—; R^(E) and R^(F) areindependently selected from the group consisting of —H, and C₁-C₄ alkyl;one of R²², R²³ is hydrogen and the other is an acid labile protectinggroup or R²² and R²³ are each hydrogen with the nitrogen to which theyare attached optionally protonated as an acid addition salt.

61D. The Drug Linker compound of embodiment 60, wherein R^(2A) issaturated C₁-C₄ alkyl or unsaturated C₃-C₄ alkyl, wherein saturatedC₁-C₄ alkyl is —CH₃, —CH₂CH₃, —CH₂CH₂CH₃ and unsaturated C₃-C₄ alkyl is—CH₂CH═CH₂ or —CH(CH₃)CH═CH₂.

62D. The Drug Linker compound of embodiment 60D wherein R^(2A) is—C(O)CH₃.

63D. The Drug Linker compound of embodiment 60D wherein R^(2A) is—CH₂CH₃.

64D. The Drug Linker compound of embodiment 60D wherein R^(2A) is—CH₂CH═CH₂.

65D. The Drug Linker compound of any one of embodiments 35D to 64Dwherein PEG has the structure selected from the group consisting of:

wherein the wavy line indicates site of attachment to X^(LP) of theParallel Connector Unit (L_(P)); R^(PEG1) is an optional PEG AttachmentUnit; R^(PEG2) is a PEG Capping Unit; R^(PEG3) is an PEG Coupling Unit;subscript n ranges from 2 to 72; each subscript n′ is independentlyselected from 1 to 72; and subscript e ranges from 2 to 5.

66D. The Drug Linker compound of embodiment 60D wherein —X^(LP)—PEG hasthe structure of:

67D. The Drug Linker compound of embodiment 66D wherein subscript n is12 and R^(PEG2) is hydrogen or —CH₃.

68D. The Drug Linker compound of embodiment 60D wherein the compound hasthe structure of:

wherein subscript u is 0 or 1; R^(7B), when present, is —OH; and R^(2A)along with the oxygen atom to which it is attached is —OC(O)CH₂,—CH₂CH₃, or —CH₂CH═CH₂.

69D. The Drug Linker compound of embodiment 68D wherein the compound hasthe structure of:

70D. A tubulysin compound having the structure of:

wherein the curved dashed line indicates optional cyclization; R^(2A) isunsaturated alkyl, optionally substituted; the circled Ar represents a5-membered nitrogen-containing heteroarylene, wherein the indicatedrequired substituents to that heteroarylene are in a 1,3-relationshipwith each other with optional substitution at the remaining positions;R³ is hydrogen or optionally substituted alkyl; R⁴, R⁵ and R⁶ areoptionally substituted alkyl, independently selected; R⁴ is hydrogen oroptionally substituted alkyl and R^(4B) is optionally substituted alkyl,or both together with the nitrogen to which they are attached, asindicated by the curved dashed line, define a quaternized nitrogenheterocycloalkyl, optionally substituted; and one R⁷ is hydrogen oroptionally substituted alkyl and the other R⁷ is optionally substitutedaralkyl or heteroaralkyl.

71D. The tubulysin compound of embodiment 70D, wherein the compound hasthe structure of:

72D. A tubulysin compound having the structure of:

wherein R^(2B) is —CH₂CH₃, —CH₂CH₂CH₃, —CH(CH₃)₂, —CH₂CH(CH₃)₂ or—CH₂C(CH₃)₃.

73D. A method of preparing a Drug Linker compound comprising the step ofquaternizing a tubulysin compound of embodiment 70D, 71D or 72D with aLinker Unit precursor.

74D. A Ligand Drug Conjugate composition, wherein the composition isrepresented by the structure of Formula D:

wherein L is an antibody Ligand Unit, thereby defining an Antibody DrugConjugate; L_(B) is a Ligand Covalent Binding Unit; L_(P) is a ParallelConnector Unit; PEG is a Polyethylene Glycol Unit; subscript a is 0 or1; subscript b is 0 or 1; A is a first optional Stretcher Unit so thatsubscript a is 0 when A is absent or A is present so that subscript a is1 and is optionally comprised of two, three or four independentlyselected subunits (A₁, A₂, A₃, A₄); B is an Branching Unit or a secondoptional Stretcher Unit (A_(O)) so that subscript b is 0 when B isabsent or B is present so that subscript b is 1 and is optionallycomprised of two, three or four subunits independently of A; subscript nis 1, 2, 3 or 4, provided that subscript b is 1 and B is a Branchingwhen subscript n is 2, 3 or 4 and provided that B is A_(O) or is absentwhen subscript n is 1; V, Z¹, Z² and Z³ are ═N— or ═C(R²⁴)—, wherein R²⁴is hydrogen or alkyl, alkenyl or alkynyl, optionally substituted, orhalogen, —NO₂, —CN or other electron withdrawing group, or —OCH₃ orother an electron donating group, or —C(R⁸)(R⁹)-D⁺, wherein at least oneof V, Z¹, and Z³ is ═C(R²⁴)—, provided that one any only one R²⁴ is—C(R⁸)(R⁹)-D⁺ so that —C(R⁸)(R⁹)-D⁺ is bonded to one of V, Z¹, and Z³when that variable group is ═C(R²⁴)—; R′ is hydrogen or —OCH₃ or otherelectron donating group; J is a heteroatom, optionally substituted whennitrogen, preferably J is —N(R²³)—, wherein R³³ is hydrogen or methyl;D+ is a quaternized tubulysin Drug Unit; W is a peptide comprised of anamino acid sequence covalently attached to J′ through an amide bondwherein that amide bond is cleavable by a protease, wherein saidprotease cleavage initiates release of a tubulysin compound (D) from aLigand Drug Conjugate compound of the composition; and subscript p is anumber ranging from 1 to 24.

75D. The Ligand Drug Conjugate composition of embodiment 74D, whereinthe composition is represented by the structure of:

wherein W consists or is comprised of a dipeptide, wherein the dipeptideis at the distal end of W and the indicated bond is an amide bondspecifically cleavable by an intracellular protease in comparison tofreely circulating serum proteases.

76D. The Ligand Drug Conjugate composition of embodiment 74D, whereinthe dipeptide has the structure of;

wherein R³⁴ is benzyl, methyl, isopropyl, isobutyl, sec-butyl,—CH(OH)CH₃ or has the structure of

and R³⁵ is methyl, —(CH₂)₄—NH₂, —(CH₂)₃NH(C═O)NH₂, (CH₂)₃NH(C═NH)NH₂, or—(CH₂)₂CO₂H, wherein the wavy line at the dipeptide N-terminus indicatescovalent binding to A_(O) or to L_(P), depending on the presence orabsence of A_(O), respectively, and the wavy line at the dipeptideC-terminus indicates covalent binding to J.

77D. The Ligand Drug Conjugate composition of embodiment 74D, 75D or 76Dwherein the quaternized tubulysin Drug Unit (-D⁺) preferably has thestructure of:

wherein the curved dashed lines indicate optional cyclizations;

R^(2A) is hydrogen or optionally substituted alkyl, or R^(2A) along withthe oxygen atom to which it is attached defines an O-linked substituentother than —OH, or R^(2A) is absent when R⁶ is bonded to that oxygenatom, as indicated by the curved dash line between R⁶ and the oxygenatom, to define an oxygen-containing heterocycloalkyl; the circled Arrepresents a 5-membered nitrogen-heteroarylene, wherein the indicatedrequired substituents to that heteroarylene are in a 1,3-relationshipwith each other with optional substitution at the remaining positions;R³ is hydrogen or optionally substituted alkyl; R⁴, R⁵ and R⁶ areoptionally substituted alkyl, independently selected, or R⁶ is bonded tothe oxygen atom of the —OR^(2A) moiety in which R^(2A) is absent and R⁴and R⁵ are as previously defined; R^(4a) is hydrogen or optionallysubstituted alkyl and R^(4B) is optionally substituted alkyl, or bothtogether with the nitrogen to which they are attached, as indicated bythe curved dotted line between R^(4A) and R^(4B), define a quaternizednitrogen heterocycloalkyl, optionally substituted; one R⁷ is hydrogen oroptionally substituted alkyl and the other R⁷ is optionally substitutedaralkyl or heteroaralkyl; wherein the wavy line indicates covalentbonding of the D⁺ structure to the remainder of the Conjugate structure.

78D. The Ligand Drug Conjugate composition of embodiment 77D wherein thequaternized tubulysin Drug Unit (-D⁺) has the structure of:

wherein subscript m is 0 or 1; Z is an optionally substituted alkyleneor an optionally substituted alkenylene; and R^(7A) is optionallysubstituted aryl or optionally substituted heteroaryl.

79D. The Ligand Drug Conjugate composition of embodiment 78D wherein thequaternized tubulysin Drug Unit -D⁺ has the structure of:

wherein R⁴ is methyl; subscript u is 0, 1 or 2; R³ is H, methyl, ethyl,propyl, —CH₂—OC(O)R^(3A), —CH₂CH(R^(3B))C(O)R^(3A) or—CH(R^(3B))C(O)NHR^(3A), wherein R^(3A) is C₁-C₆ alkyl and R^(3B) is Hor C₁-C₆ alkyl, independently selected from R^(3A); R^(2A) along withthe oxygen atom to which it is attached is an O-linked substituentselected from the group consisting of —OCH₂OCH₂R^(2B), —OCH₂R^(2B),—OC(O)R^(2B), —CH₂OC(O)R^(2B), —OC(O)N(R^(2B))(R^(2C)), and—OCH₂C(O)N(R^(2B))(R^(2C)), wherein R^(2B) and R^(2C) (are independentlyselected from the group consisting of H, C₁-C₆ alkyl and C₂-C₆ alkenyl;and each R^(7B), when present, independently is —OH or —OCH₃.

80D. The Ligand Drug Conjugate composition of embodiment 79D, whereinthe quaternized tubulysin Drug Unit has the structure of:

wherein R^(2B) is —CH₃, —CH₂CH₃, —CH₂CH₂CH₃, —CH(CH₃)₂, —CH₂CH(CH₃)₂,—CH₂C(CH₃)₃.

81D. The Ligand Drug Conjugate composition of embodiment 80D, whereinthe quaternized tubulysin Drug Unit has the structure of:

wherein R^(2B) is hydrogen, methyl or —OCH₃, or —OCH₂R^(2B) is—OCH₂CH═CH₂ or —OCH₂C(CH₃)═CH₂.

82D. The Ligand Drug Conjugate composition of embodiment 74D, wherein acompound thereof is represented by the structure of:

83D. A Drug Linker compound, wherein the compound is represented by thestructure of:

wherein L_(B)′ is a Ligand Covalent Binding Unit precursor, L_(P) is aParallel Connector Unit; PEG is a Polyethylene Glycol Unit; subscript ais 0 or 1; subscript b is 0 or 1; A is a first optional Stretcher Unitso that subscript a is 0 when A is absent or A is present so thatsubscript a is 1 and is optionally comprised of two, three or fourindependently selected subunits (A₁, A₂, A₃, A₄); B is an Branching Unitor a second optional Stretcher Unit (A_(O)) so that subscript b is 0when B is absent or B is present so that subscript b is 1 and isoptionally comprised of two, three or four subunits independently of A;subscript n is 1, 2, 3 or 4, provided that subscript b is 1 and B is aBranching when subscript n is 2, 3 or 4 and provided that B is A_(O) oris absent when subscript n is 1; V, Z¹, Z² and Z³ are ═N— or ═C(R²⁴)—,wherein R²⁴ is hydrogen or alkyl, alkenyl or alkynyl, optionallysubstituted, or halogen, —NO₂, —CN or other electron withdrawing group,or —OCH₃ or other an electron donating group, or —C(R$)(R⁹)-D⁺, whereinat least one of V, Z¹, and Z³ is ═C(R²⁴)—, provided that one any onlyone R⁴ is —C(R⁸)(R⁹)-D⁺ so that —C(R⁸)(R⁹)-D⁺ is bonded to one of V, Z¹,and Z³ when that variable group is ═C(R²⁴)—; R′ is hydrogen or —OCH₃ orother electron donating group; D+ is a quaternized tubulysin Drug Unit;J is a heteroatom, optionally substituted when nitrogen, preferably J is—N(R³³)—, wherein R³³ is hydrogen or methyl; W is a peptide comprised ofan amino acid sequence covalently attached to J through an amide bondwherein that amide bond is cleavable by a protease, wherein saidprotease cleavage initiates release of a tubulysin compound (D) from theDrug Linker compound or from a Ligand Drug Conjugate compound preparedfrom the Drug Linker compound, wherein the Ligand Drug Conjugatecompound has the Formula 1D structure of embodiment 74D in whichsubscript p is replaced by subscript p′, wherein subscript p′ is aninteger ranging from 1 to 24.

84D. The Drug Linker compound of embodiment 83D, wherein the compound isrepresented by the structure of:

wherein W consists or is comprised of a dipeptide, wherein the dipeptideis at the distal end of W and the indicated bond is an amide bondspecifically cleavable by an intracellular protease in comparison tofreely circulating serum proteases.

85D. The Drug Linker compound of embodiment 84D, wherein the dipeptidehas the structure of;

wherein R³⁴ is benzyl, methyl, isopropyl, isobutyl, sec-butyl,—CH(OH)CH₃ or has the structure of

and R³⁵ is methyl, —(CH₂)₄—NH₂, —(CH₂)₃NH(C═O)NH₂, (CH₂)₃NH(C═NH)NH₂, or—(CH₂)₂CO₂H, wherein the wavy line at the dipeptide N-terminus indicatescovalent binding to A_(O) or L_(P), depending on the presence or absenceof A_(O), respectively, and the wavy line at the dipeptide C-terminusindicates covalent bonding to the nitrogen atom of said amide bond.

86D. The Drug Linker compound of embodiment 83D, 84D or 85D wherein thequaternized tubulysin Drug Unit (-D⁺) preferably the structure of:

wherein the curved dashed lines indicate optional cyclizations; R^(2A)is hydrogen or optionally substituted alkyl, or R^(2A) along with theoxygen atom to which it is attached defines an O-linked substituentother than —OH, or R^(2A) is absent when R⁶ is bonded to that oxygenatom, as indicated by the curved dash line between R⁶ and the oxygenatom, to define an oxygen-containing heterocycloalkyl; the circled Arrepresents a 5-membered nitrogen-heteroarylene, wherein the indicatedrequired substituents to that heteroarylene are in a 1,3-relationshipwith each other with optional substitution at the remaining positions;R³ is hydrogen or optionally substituted alkyl; R⁴, R⁵ and R⁶ areoptionally substituted alkyl, independently selected, or R⁶ is bonded tothe oxygen atom of the —OR^(2A) moiety in which R^(2A) is absent and R⁴and R⁵ are as previously defined; R^(4a) is hydrogen or optionallysubstituted alkyl and R^(4B) is optionally substituted alkyl, or bothtogether with the nitrogen to which they are attached, as indicated bythe curved dotted line between R^(4A) and R^(4B), define a quaternizednitrogen heterocycloalkyl, optionally substituted; one R⁷ is hydrogen oroptionally substituted alkyl and the other R⁷ is optionally substitutedaralkyl or heteroaralkyl; wherein the wavy line indicates covalentbonding of the D⁺ structure to the remainder of the Drug Linker compoundstructure.

87D. The Drug Linker compound of embodiment 86D wherein the quaternizedtubulysin Drug Unit (-D⁺) has the structure of:

subscript m is 0 or 1; Z is an optionally substituted alkylene or anoptionally substituted alkenylene; and R^(7A) is optionally substitutedaryl or optionally substituted heteroaryl.

88D. The Drug Linker compound of embodiment 87D wherein the quaternizedtubulysin Drug Unit (-D⁺) has the structure of:

wherein R^(7A) is optionally substituted phenyl and R⁸ is hydrogen ormethyl.

89D. The Drug Linker compound of embodiment 88D wherein the quaternizedtubulysin Drug Unit (-D⁺) has the structure of:

wherein R⁴ is methyl; subscript u is 0, 1 or 2; R³ is H, methyl, ethyl,propyl, —CH₂—OC(O)R^(3A), —CH₂CH(R^(3B))C(O)R^(3A) or—CH(R^(3B))C(O)NHR^(3A), wherein R^(3A) is C₁-C₆ alkyl and R^(3B) is Hor C₁-C₆ alkyl, independently selected from R^(3A); R^(2A) along withthe oxygen atom to which it is attached is an O-linked substituentselected from the group consisting of —OCH₂OCH₂R^(2B), —OCH₂R^(2B),—OC(O)R^(2B), —CH₂OC(O)R^(2B), —OC(O)N(R^(2B))(R^(2C)), and—OCH₂C(O)N(R^(2B))(R^(2C)), wherein R^(2B) and R^(2C) are independentlyselected from the group consisting of H, C₁-C₆ alkyl and C₂-C₆ alkenyl;and each R^(7B), when present, independently is —OH or —OCH₃.

90D. The Drug Linker compound of embodiment 89D, wherein the quaternizedtubulysin Drug Unit (-D⁺) has the structure of:

wherein R^(2B) is —CH₃, —CH₂CH₃, —CH₂CH₂CH₃, —CH(CH₃)₂, —CH₂CH(CH₃)₂,—CH₂C(CH₃)₃.

91D. The Drug Linker compound of embodiment 89D, wherein the quaternizedtubulysin Drug Unit (-D⁺) has the structure of:

wherein R^(2B) is hydrogen, methyl or —OCH₃, or —OCH₂R^(2B) is—OCH₂CH═CH₂ or —OCH₂C(CH₃)═CH₂.

92D. The Drug Linker compound of embodiment 83D, wherein the compoundhas the structure of:

wherein one of R²², R²³ is hydrogen and the other is an acid labileprotecting group or R²² and R²³ are each hydrogen with the nitrogen towhich they are attached optionally protonated as an acid addition salt.

93D. A formulation comprising a Ligand Drug Conjugate of any one ofembodiments 1D to 34D and 78D to 86D and one or more excipients.

94D. The formulation of embodiment 93D wherein the formulation is apharmaceutically acceptable formulation or a precursor thereof.

95D. The formulation of embodiment 94D wherein the pharmaceuticallyacceptable formulation precursor is a solid suitable for reconstitutionas a solution for intravenous injection to a subject.

96D. The formulation of embodiment 94D wherein the pharmaceuticallyacceptable formulation is a liquid suitable for intravenous injection toa subject.

97D. The formulation of embodiments 94D, 95D or % D wherein the LigandDrug Conjugate is present in the pharmaceutically acceptable formulationor precursor thereof in an effective amount for treatment of ahyperproliferative condition.

98D. A method of treating a hyperproliferative disease or conditioncomprising the step of administering to a patient having said disease orcondition an effective amount of a Ligand Drug Conjugate of any one ofembodiments 1D to 34D and 74D to 82D.

99D. The method of embodiment 98D wherein the hyperproliferative diseaseor condition is a cancer.

100D. The method of embodiment 98D wherein the hyperproliferativedisease or condition is a leukemia or a lymphoma.

101D. A method of inhibiting the multiplication of a tumor cell orcancer cell, or causing apoptosis in a tumor or cancer cell, by exposingsaid cell with an effective amount of Ligand Drug Conjugate of any oneof embodiments 1D to 34D and 74D to 82D or of a tubulysin compound ofany one of embodiments 70D to 72D.

Examples

General Information. All commercially available anhydrous solvents wereused without further purification. Analytical thin layer chromatographywas performed on silica gel 60 F254 aluminum sheets (EMD Chemicals,Gibbstown, N.J.). Radial chromatography was performed on Chromatotronapparatus (Harris Research, Palo Alto, Calif.). Column chromatographywas performed on a Biotage Isolera One flash purification system(Charlotte, N.C.). Analytical HPLC was performed on a Varian ProStar 210solvent delivery system configured with a Varian ProStar 330 PDAdetector. Samples were eluted over a C12 Phenomenex Synergi 2.0×150 mm,4 μm, 80 Å reverse-phase column. The acidic mobile phase consisted ofacetonitrile and water both containing either 0.05% trifluoroacetic acidor 0.1% formic acid (denoted for each compound). Compounds were iseluted with a linear gradient of acidic acetonitrile from 5% at 1 minpost injection, to 95% at 11 min, followed by isocratic 95% acetonitrileto 15 min (flow rate=1.0 mL/min). LC-MS was performed on two differentsystems. LC-MS system 1 consisted of a ZMD Micromass mass spectrometerinterfaced to an HP Agilent 1100 HPLC instrument equipped with a C12Phenomenex Synergi 2.0×150 mm, 4 μm, 80 Å reverse phase column. Theacidic eluent consisted of a linear gradient of acetonitrile from 5% to95% in 0.1% aqueous formic acid over 10 min, followed by isocratic 95%acetonitrile for 5 min (flow rate=0.4 mL/min). LC-MS system 2 consistedof a Waters Xevo G2 ToF mass spectrometer interfaced to a Waters 2695Separations Module with a Waters 2996 Photodiode Array Detector; thecolumn, mobile phases, gradient, and flow rate were same as for LC-MSsystem 1. UPLC-MS system 1 consisted of a Waters SQ mass detectorinterfaced to an Acquity Ultra Performance LC equipped with an AcquityUPLC BEH C18 2.1×50 mm, 1.7 μm reverse phase column. The acidic mobilephase (0.1% formic acid) consisted of a gradient of 3% acetonitrile/97%water to 100% acetonitrile (flow rate=0.5 mL/min). UPLC-MS system 2consisted of a Waters Xevo G2 ToF mass spectrometer interfaced to aWaters Acquity H-Class Ultra Performance LC equipped with an AcquityUPLC BEH C18 2.1×50 mm, 1.7 μm reverse phase column. The acidic mobilephase (0.1% formic acid) consisted of a gradient of 3% acetonitrile/97%water to 100% acetonitrile (flow rate=0.7 mL/min). Preparative HPLC wascarried out on a Varian ProStar 210 solvent delivery system configuredwith a Varian ProStar 330 PDA detector. Products were purified over aC12 Phenomenex Synergi 10.0×250 mm, 4 μm, 80 Å reverse phase columneluting with 0.1% trifluoroacetic acid in water (solvent A) and 0.1%trifluoroacetic acid in acetonitrile (solvent B). The purificationmethods generally consisted of linear gradients of solvent A to solventB, ramping from 90% aqueous solvent A to 10% solvent A. The flow ratewas 4.6 mL/min with monitoring at 254 nm. NMR spectral data werecollected on a Varian Mercury 400 MHz spectrometer. Coupling constants(J) are reported in hertz.

(S)-2-((S)-2-((tert-butoxycarbonyl)amino)-3-methylbutanamido)-propanoicacid (3): A flask was charged with Boc-Val-OSu (1, 1.0 g, 3.18 mmol) andH-Ala-OH (2, 312 mg, 3.5 mmol) in anhydrous dimethylformamide (10.6 mL).N,N-diisopropylethylamine (1.1 mL, 6.4 mmol) was added and the solutionwas stirred under N₂ at 50° C. for 12 hours. The reaction was taken upin DMSO and purified by preparative HPLC to yield 3 (808 mg, 88%).Analytical UPLC-MS (system 1): t_(r)=1.38 min, m/z (ES+) found 289.60.

tert-butyl((S)-1-(((S)-1-((4-(hydroxymethyl)phenyl)amino)-1-oxopropan-2-yl)amino)-3-methyl-1-oxobutan-2-yl)carbamate(5): A flame-dried flask was charged with dipeptide 3 (808 mg, 2.8 mmol)and 4-aminobenzoic alcohol 4 (345 mg, 2.8 mmol) in anhydrousdichloromethane (14 mL). EEDQ (762 mg, 3.1 mmol) was added as a solidand stirred under nitrogen at room temperature for 12 h. The reactionwas then condensed and purified over silica via a Biotage column(CH₂Cl₂/MeOH, 0%-10%) to provide 5 (660 mg, 60%). Analytical UPLC-MS(system 1): t_(r)=1.51 min, m/z (ES+) found 394.51.

tert-butyl((S)-1-(((S)-1-((4-(bromomethyl)phenyl)amino)-1-oxopropan-2-yl)amino)-3-methyl-1-oxobutan-2-yl)carbamate(6): A flask containing Boc-Val-Ala-PABA-OH (5, 100 mg, 254 μmol),N-bromosuccinimide (68 mg, 381 μmol), and triphenylphosphine (100 mg,381 μmol) was flushed with nitrogen. The reaction was taken up in THF (4mL) and stirred for 12 hours. The reaction was condensed and purifiedover silica via a Biotage column (Hexanes/EtOAc, 10%-100%) to provide 6(94 mg, 81%). Analytical UPLC-MS (system 1): t_(r)=2.09 min, m/z (ES+)found 456.10.

(2S,4R)-tert-butyl4-(2-((1R,3R)-1-acetoxy-3-((2S,3S)—N,3-dimethyl-2-((R)-1-methylpiperidine-2-carboxamido)pentanamido)-4-methylpentyl)thiazole-4-carboxamido)-2-methyl-5-phenylpentanoate(8): A flame A flame dried flask was charged with a tubulysin analog (7,10 mg, 14 μmol) in anhydrous DCM (0.7 mL) and t-butanol (0.7 mL).Diisopropylcarbodiimide (3.2 μL, 21 μmol) and DMAP (0.08 mg, 0.7 μmol)were added and the reaction was stirred at room temperature for 48hours. The reaction was condensed, taken up in DMSO, and purified bypreparative HPLC to yield 8 (3.5 mg, 32%). Analytical UPLC-MS (system1): t_(r)=1.35 min, m/z (ES+) found 784.56.

(2R)-2-(((2S,3S)-1-(((1R,3R)-1-acetoxy-1-(4-(((2R,4S)-5-(tert-butoxy)-4-methyl-5-oxo-1-phenylpentan-2-yl)carbamoyl)thiazol-2-yl)-4-methylpentan-3-yl)(methyl)amino)-3-methyl-1-oxopentan-2-yl)carbamoyl)-1-(4-((S)-2-((S)-2-((tert-butoxycarbonyl)amino)-3-methylbutanamido)propanamido)benzyl)-1-methylpiperidin-1-ium(9): A pressure vessel was charged with Boc-Val-Ala-PAB-Br (6, 3.5 mg,7.7 μmol) and protected tubulysin 8 (4.0 mg, 5.1 μmol) in anhydrousbutanone (0.765 mL). N,N-diisopropylethylamine was added (1.8 μL, 10μmol) and the reaction was flushed with nitrogen. The vessel was sealedand allowed to stir at 80° C. for 12 hours. The reaction was condensed,taken up in DMSO, and purified by preparative HPLC to yield 9 (3.5 mg,58%). Analytical UPLC-MS (system 1): t_(r)=1.51 min, m/z (ES+) found1159.58.

(2R)-2-(((2S,3S)-1-(((1R,3R)-1-acetoxy-1-(4-(((2R,4S)-4-carboxy-1-phenylpentan-2-yl)carbamoyl)thiazol-2-yl)-4-methylpentan-3-yl)(methyl)amino)-3-methyl-1-oxopentan-2-yl)carbamoyl)-1-(4-((S)-2-((S)-2-amino-3-methylbutanamido)propanamido)benzyl)-1-methylpiperidin-1-ium(10): A flask containing Boc-Val-Ala-PAB-TubM-OtBu (9, 3.5 mg, 3 μmol)was cooled to 0° C. under nitrogen. A solution of 10% TFA in CH₂Cl₂ (0.3mL) was added dropwise and stirred for 4 hours. The reaction wascondensed, taken up in DMSO, and purified by preparative HPLC to yield10 (1.9 mg, 63%). Analytical UPLC-MS (system 1): t_(r)=1.05 min, m/z(ES+) found 1003.60.

(2R)-2-(((2S,3S)-1-(((1R,3R)-1-acetoxy-1-(4-(((2R,4S)-4-carboxy-1-phenylpentan-2-yl)carbamoyl)thiazol-2-yl)-4-methylpentan-3-yl)(methyl)amino)-3-methyl-1-oxopentan-2-yl)carbamoyl)-1-(4-((S)-2-((S)-2-(6-(2,5-dioxo-2,5-dihydro-1H-pyrrol-1-yl)hexanamido)-3-methylbutanamido)propanamido)benzyl)-1-methylpiperidin-1-ium(12): MC-OSu (11, 0.6 mg, 2 μmol) was taken up in anhydrousdimethylformamide (0.2 mL) and added to a flask containingVal-Ala-PAB-Tub (10, 1.9 mg, 2 μmol). N,N-diisopropylethylamine (1.0 mg,8 μmol) was added and the reaction was stirred under nitrogen for 3hours. The reaction was taken up in DMSO, and purified by preparativeHPLC to yield quaternary amine tubulysin linker 12 (1.2 mg, 53%).Analytical UPLC-MS (system 1): t_(r)=1.25 min, m/z (ES+) found 1196.45.

(2R)-2-(((2S,3S)-1-(((1R,3R)-1-acetoxy-1-(4-(((2R,4S)-4-carboxy-1-phenylpentan-2-yl)carbamoyl)thiazol-2-yl)-4-methylpentan-3-yl)(methyl)amino)-3-methyl-1-oxopentan-2-yl)carbamoyl)-1-(4-((7S,10S,13S)-7-(2,5-dioxo-2,5-dihydro-1H-pyrrol-1-yl)-10-isopropyl-2,2,13-trimethyl-4,8,11-trioxo-3-oxa-5,9,12-triazatetradecanamido)benzyl)-1-methylpiperidin-1-ium(14): MDPR(Boc)-OSu (13, 1.3 mg, 3.5 μmol) was taken up in anhydrousdimethylformamide (0.3 mL) and added to a flask containingVal-Ala-PAB-TubM (10, 3.2 mg, 3.2 μmol). N,N-diisopropylethylamine (1.6mg, 13 μmol) was added and the reaction was stirred under nitrogen for 3hours. The reaction was taken up in DMSO, and purified by preparativeHPLC to yield 14 (2.0 mg, 49%). Analytical UPLC-MS (system 2):t_(r)=1.35 min, m/z (ES+) found 1269.76.

(2R)-2-(((2S,3S)-1-(((1R,3R)-1-acetoxy-1-(4-(((2R,4S)-4-carboxy-1-phenylpentan-2-yl)carbamoyl)thiazol-2-yl)-4-methylpentan-3-yl)(methyl)amino)-3-methyl-1-oxopentan-2-yl)carbamoyl)-1-(4-((S)-2-((S)-2-((S)-3-amino-2-(2,5-dioxo-2,5-dihydro-1H-pyrrol-1-yl)propanamido)-3-methylbutanamido)propanamido)benzyl)-1-methylpiperidin-1-ium(15): A flask containing MDPR(Boc)-Val-Ala-PAB-TubM (14, 2 mg, 1.6 μmol)was cooled to 0° C. under nitrogen. A solution of 10% TFA in CH₂Cl₂ (1.6mL) was added dropwise and stirred for 4 hours. The reaction wascondensed, taken up in DMSO, and purified by preparative HPLC to yield15 (1.0 mg, 54%). Analytical UPLC-MS (system 2): t_(r)=1.02 min, m/z(ES+) found 1169.72.

Tubulysin analogs in which the tubuvaline acetate was replaced with analkyl ether were prepared as shown in Schemes 3.

General procedure for the etherification of tubuvaline. A flame-driedflask was charged with the Boc-protected known tubuvaline (J. Org.Chem., 2008, 73, 4362-4369) intermediate 17 in anhydrous tetrahydrofuran(50 mM), to which was added 18-crown-6 (2.0 equivalents) and cooled to−78 C. Potassium hexamethyldisilazide (1.5 equivalents) as a 1 Msolution in tetrahydrofuran was added dropwise and the reaction was thenstirred for 1 hour at −78 C under nitrogen. Iodoalkane (2-5 equivalents)was then added and the reaction slowly warmed to room temperature andfollowed by UPLC/MS. Once the starting material was consumed, thereaction was cooled on ice and quenched with saturated ammonium chlorideand diluted in dichloromethane (10 volumes). The organic layer waswashed with 0.1 M HCl and the resulting aqueous phase extracted twicewith dichloromethane. The combined organics were then dried over sodiumsulfate, filtered, and concentrated to dryness. Purification of thecrude O-alkylated products was achieved by flash chromatography oversilica gel or preparative HPLC.

Ethyl2-((1R,3R)-3-((tert-butoxycarbonyl)(methyl)amino)-1-methoxy-4-methylpentyl)thiazole-4-carboxylate(18): Tubuvaline intermediate 17 (170 mg, 440 μmol) was O-methylated asdescribed above with iodomethane (89 μl, 880 μmol) to provide 170 mg(97%) of the title compound after silica gel purification elutingmethanol and dichloromethane mixtures. UPLC-MS (system 2): t_(r)=1.62min, m/z (ES+) calculated 401.21, found 401.28.

Ethyl2-((1R,3R)-3-((tert-butoxycarbonyl)(methyl)amino)-1-ethoxy-4-methylpentyl)thiazole-4-carboxylate(19): Tubuvaline intermediate 17 (392 mg, 1.01 mmol) was O-ethylated asdescribed above with iodoethane (791 mg, 5.05 mmol) to provide 407 mg(97%) of the title compound after silica gel purification elutingmethanol and dichloromethane mixtures. UPLC-MS (system 2): t_(r)=1.66min. m/z (ES+) calculated 415.23 (M+H)⁺, found 415.29.

Ethyl2-((1R,3R)-3-((tert-butoxycarbonyl)(methyl)amino)-4-methyl-1-propoxypentyl)thiazole-4-carboxylate(20): Tubuvaline intermediate 17 (22 mg, 57 μmol) was O-propylated asdescribed above with 1-iodopropane (28 μl, 285 μmol) to provide 9 mg(37%) of the title compound after purification by preparative HPLC.UPLC-MS (system 2): t_(r)=1.77 min, m/z (ES+) calculated 428.23 (M+H)⁺,found 451.30 (M+Na)⁺. ¹H NMR (1:1 mix of rotamers, CDCl₃) δ (ppm) 0.91(m, 9H), 1.40 (t, J=7.0 Hz, 3H), 1.47 (two s from rotamers, 9H), 1.64(m, 3H), 1.87 (m, 2H), 2.74 (m, 3H), 3.42 (m, 2H), 4.10 (m, 1H), 4.42(q, J=7.0 Hz, 2H), 4.50 (m, 1H), 8.14 (two s from rotamers, 1H).

General procedure for the saponification of O-alkylated tubuvalineesters. Saponification reactions were carried out at 20 mM reactionconcentration using a 1:1:1 mixture of tetrahydrofuran:methanol:watersolvent mixture. O-alkylated tubuvaline intermediates 18-20 weredissolved in 1 volume each tetrahydrofuran and methanol. The mixture wasthen cooled in an ice bath at 0 C. Lithium hydroxide monohydrate (2-3equivalents) was dissolved in 1 volume of distilled water and addeddropwise to the reaction flask, with stirring at 0 C. The reaction wasthen allowed to warm up to room temperature and monitored by UPLC/MS.Once the starting material had converted to free acid, the reaction wasquenched with glacial acetic acid (2-3 equivalents) and concentrated byrotary evaporation. The crude carboxylic acids were then purified bypreparative HPLC.

Ethyl2-((1R,3R)-3-((tert-butoxycarbonyl)(methyl)amino)-1-methoxy-4-methylpentyl)thiazole-4-carboxylate(21): Tubuvaline methyl ether intermediate 18 (170 mg, 425 μmol) wassaponified as described above with lithium hydroxide monohydrate (19 mg,1.28 mmol) to provide 140 mg (89%) of the title compound. UPLC-MS(system 1): t_(r)=1.47 min, m/z (ES+) calculated 373.18, found 373.41.¹H NMR (1:1 mix of rotamers, CDCl₃) δ (ppm) 0.87 (dd, J=6.7, 2.0 Hz,3H), 0.96 (dd. J=6.7, 1.2 Hz, 3H), 1.49 (two s from rotamers, 9H), 1.67(m, 1H), 1.85 (m, 1H), 2.01 (m, 1H), 2.70 (m, 3H), 3.41 (s, 3H), 4.12(m, 1H), 4.36 (first rotamer, dd, J=10.5, 2.3 Hz, 0.5H), 4.48 (secondrotamer, d, J=8.6 Hz, 0.5H), 8.28 (two s from rotamers, 1H).

Ethyl2-((1R,3R)-3-((tert-butoxycarbonyl)(methyl)amino)-1-ethoxy-4-methylpentyl)thiazole-4-carboxylate(22): Tubuvaline ethyl ether intermediate 19 (170 mg, 425 μmol) wassaponified as described above with lithium hydroxide monohydrate (19 mg,1.28 mmol) to provide 140 mg (89%) of the title compound. UPLC-MS(system 2): t_(r)=1.48 min, m/z (ES+) calculated 387.20 (M+H)⁺, found387.26. ¹H NMR (CDCl₃) δ (ppm) 0.88 (dd, J=6.7, 2.0 Hz, 3H), 0.96 (d,J=6.6 Hz, 3H), 1.49 (two s from rotamers, 9H), 1.68 (m, 1H), 1.86 (m,1H), 2.00 (m, 1H), 2.69 (m, 3H), 3.53 (m, 2H), 4.09 (m, 1H), 4.43 (firstrotamer, dd. J=10.2, 2.7 Hz, 0.5H), 4.54 (second rotamer, d, J=7.0 Hz,0.5H), 8.24 (two s from rotamers, 1H).

Ethyl2-((1R,3R)-3-((tert-butoxycarbonyl)(methyl)amino)-4-methyl-1-propoxypentyl)thiazole-4-carboxylate(23): Tubuvaline propyl ether intermediate 20 (9 mg, 20 μmol) wassaponified as described above with lithium hydroxide monohydrate (1.7mg, 40 μmol) to provide 7.6 mg (95%) of the title compound. UPLC-MS(system 2): t_(r)=1.58 min, m/z (ES+) calculated 401.21 (M+H)⁺, found401.28 (M+Na)⁺.

General procedure for the amide coupling of O-alkylated tubuvaline freeacids and tubuphenylalanine allyl ester. O-alkylated tubuvaline freeacids 21-23 were pre-activated by dissolution in anhydrousdimethylformamide (25-50 mM) and addition of HATU (2.4 equivalents) andDIPEA (5 equivalents); the mixture was then stirred under nitrogen atroom temperature for 10 minutes. The activated acid was then added tothe known (Org. Lett., 2007, 9, 1605-1607) tubuphenylalanine allyl ester16 and the reaction was then stirred at an ambient temperature undernitrogen, with progress monitored by UPLC/MS. Upon reaction completion,glacial acetic acid (14 equivalents) was then added and the product waspurified by preparative HPLC.

(2S,4R)-allyl4-(2-((1R,3R)-3-((tert-butoxycarbonyl)(methyl)amino)-1-methoxy-4-methylpentyl)thiazole-4-carboxamido)-2-methyl-5-phenylpentanoate(24): Tubuvaline methyl ether (TuvOMe) intermediate 21 (140 mg, 380 μmolwas coupled to tubuphenylalanine (Tup) allyl ester 16 (188 mg, 760 μmol)to provide 164 mg (72%) of the title compound. UPLC-MS (system 1):t_(r)=1.96 min, m/z (ES+) calculated 602.33 (M+H)⁺, found 602.26.

(2S,4R)-allyl4-(2-((1R,3R)-3-((tert-butoxycarbonyl)(methyl)amino)-1-ethoxy-4-methylpentyl)thiazole-4-carboxamido)-2-methyl-5-phenylpentanoate(25): Tubuvaline ethyl ether (TuvOEt) intermediate 22 (140 mg, 380 μmol)was coupled to tubuphenylalanine (Tup) allyl ester 16 (188 mg, 760 μmol)to provide 164 mg (72%) of the title compound. UPLC-MS (system 2):t_(r)=1.84 min, m/z (ES+) calculated 616.34 (M+H)⁺, found 616.43.

(2S,4R)-allyl4-(2-((1R,3R)-3-((tert-butoxycarbonyl)(methyl)amino)-4-methyl-1-propoxypentyl)thiazole-4-carboxamido)-2-methyl-5-phenylpentanoate(26): Tubuvaline propyl ether (TuvOPr) intermediate 23 (7.6 mg, 19 μmol)was coupled to tubuphenylalanine (Tup) allyl ester 16 (9.4 mg, 38 μmol)to provide 8 mg (67%) of the title compound. UPLC-MS (system 2):t_(r)=2.00 min, m/(ES+) calculated 630.36 (M+H)⁺, found 630.45. ¹H NMR(CDCl₃) δ (ppm) 0.94 (m, 9H), 1.19 (d, J=7.4 Hz, 3H), 1.49 (s, 9H), 1.64(m, 5H), 1.84 (m, 1H), 2.03 (m, 2H), 2.63 (m, 1H), 2.73 (m, 3H), 2.93(m, 2H), 3.41 (m, 2H), 4.07 (m, 2H), 4.29 (m, 1H), 4.41 (m, 2H), 4.55(m, 2H), 5.25 (m, 2H), 5.88 (m, 1H), 7.24 (m, 5H), 8.05 (two s fromrotamers, 1H).

General procedure for the Boc deprotection of Tuv(O-Alk)-TupIntermediates. O-alkylated tubuvaline-tubuphenylalanine intermediates24-26 were deprotected to reveal the secondary amine functional groupunder acidic conditions with 10% TFA in dichloromethane (25 mM).Specifically, the starting material was dissolve in anhydrousdichloromethane (9 volumes) and stirred under nitrogen at 0 C.Trifluoroacetic acid (1 volume) was then added dropwise to the stirredsolution. The reaction was warmed slowly to room temperature andmonitored by UPLC/MS. Upon completion, the reaction was concentrated byrotary evaporation and pumped down on a vacuum line overnight. The freeamines 27-29 were carried forward without further purification.

(2S,4R)-allyl4-(2-((1R,3R)-1-methoxy-4-methyl-3-(methylamino)pentyl)thiazole-4-carboxamido)-2-methyl-5-phenylpentanoate(27): Boc-protected TuvOMe-Tup intermediate 24 (160 mg, 267 μmol) wasdeprotected as described above to provide 133 mg (99%) of the titlecompound. UPLC-MS (system 1): t, =1.17 min, m/z (ES+) calculated 524.26(M+Na)⁺, found 524.27.

(2S,4R)-allyl4-(2-((1R,3R)-1-ethoxy-4-methyl-3-(methylamino)pentyl)-thiazole-4-carboxamido)-2-methyl-5-phenylpentanoate(28): Boc-protected TuvOEt-Tup intermediate 25 (160 mg, 267 μmol) wasdeprotected as described above to provide 133 mg (99%) of the titlecompound. UPLC-MS (system 2): t_(r)=1.11 min, m/z (ES+) calculated516.29 (M+H)⁺, found 516.37.

(2S,4R)-allyl2-methyl-4-(2-((1R,3R)-4-methyl-3-(methylamino)-1-propoxypentyl)thiazole-4-carboxamido)-5-phenylpentanoate(29): Boc-protected TuvOEt-Tup intermediate 26 (8 mg, 13 μmol) wasdeprotected as described above to provide 7 mg (quant.) of the titlecompound. UPLC-MS (system 2): t_(r)=1.16 min, m/z (ES+) calculated530.31 (M+H)⁺, found 530.40.

General procedure for the amide coupling of O-alkylatedtubuvaline-tubuphenylalanine dipeptides with Fmoc-protectedL-isoleucine. Commercially available Fmoc-L-Isoleucine (1.3-2equivalents) was dissolved in anhydrous dimethylformamide (50-200 mM)and pre-activated with HATU (1.5-2 equivalents) and DIPEA (2equivalents); the mixture was stirred for 10 minutes at room temperatureunder nitrogen. The activated acid was then added to theTuv(O-ether)-Tup dipeptides 27-29; the reaction was stirred at roomtemperature under nitrogen and monitored by UPLC/MS. Once the reactionhad stopped progressing or had reached completion, glacial acetic acid(13 equivalents) was added and the reaction was purified by prep HPLC.

(2S,4R)-allyl4-(2-((5S,8R,10R)-5-((S)-sec-butyl)-1-(9H-fluoren-9-yl)-8-isopropyl-7-methyl-3,6-dioxo-2,11-dioxa-4,7-diazadodecan-10-yl)thiazole-4-carboxamido)-2-methyl-5-phenylpentanoate(30): TuvOMe-Tup intermediate 27 (160 mg, 265 μmol) was coupled toFmoc-L-Ile as described above to provide 67 mg (30%) of the titlecompound. UPLC-MS (system 1): t_(r)=2.07 min, m/z (ES+) calculated837.43 (M+H)⁺, found 837.20.

(2S,4R)-allyl 4-(2-4(5S,8R,10R)-5-((S)-sec-butyl)-1-49H-fluoren-9-yl)-8-Isopropyl-7-methyl-3,6-dioxo-2,11-dioxa-4,7-diazatridecan-10-yl)thiazole-4-carboxamido)-2-methyl-5-phenylpentanoate(31): TuvOEt-Tup intermediate 28 (160 mg, 265 μmol) was coupled toFmoc-L-Ile as described above to provide 133 mg (99%) of the titlecompound. UPLC-MS (system 2): t_(r)=1.95 min, m/z (ES+) calculated851.44 (M+H)⁺, found 851.54.

(2S,4R)-allyl4-(2-((5S,8R,10R)-5-((S)-sec-butyl)-1-(9H-fluoren-9-yl)-8-isopropyl-7-methyl-3,6-dioxo-2,11-dioxa-4,7-diazatetradecan-10-yl)thiazole-4-carboxamido)-2-methyl-5-phenylpentanoate(32): TuvOPr-Tup intermediate 29 (7 mg, 13 μmol) was coupled toFmoc-L-Ile as described above to provide 9 mg (82%) of the titlecompound. UPLC-MS (system 2): t_(r)=2.25 min, m/z (ES+) calculated865.46 (M+H)⁺, found 865.65.

General procedure for the Fmoc-deprotection of isoleucine-O-alkylatedtubuvaline-tubuphenylalanine tripeptides. Fmoc-Ile-Tuv(O-ether)-Tupallyl ester (30-32) was treated with 20% piperidine in dimethylformamide(20 mM), with stirring under nitrogen at room temperature. Once completedeprotection had been achieved, as monitored by UPLC/MS, the reactionmixture was concentrated by rotary evaporation. The crude product wasthen purified by preparative HPLC to provide free amine tripeptides33-35.

(2S,4R)-allyl4-(2-((1R,3R)-3-((2S,3S)-2-amino-N,3-dimethyl-pentanamido)-1-methoxy-4-methylpentyl)thiazole-4-carboxamido)-2-methyl-5-phenylpentanoate(33): Fmoc-Ile-TuvOMe-Tup intermediate 30 (67 mg, 80 μmol) wasdeprotected as described above to provide 30 mg (61%) of the titlecompound. UPLC-MS (system 1): t_(r)=1.30 min, m/z (ES+) calculated637.34 (M+Na)⁺, found 637.57.

(2S,4R)-allyl4-(2-((1R,3R)-3-((2S,3S)-2-amino-N,3-dimethyl-pentanamido)-1-ethoxy-4-methylpentyl)thiazole-4-carboxamido)-2-methyl-5-phenylpentanoate(34): Fmoc-Ile-TuvOEt-Tup intermediate 31 (67 mg, 80 μmol) wasdeprotected as described above to provide 30 mg (61%) of the titlecompound. UPLC-MS (system 2): t_(r)=1.18 min, m/z (ES+) calculated629.38 (M+H)⁺, found 629.45.

(2S,4R)-allyl4-(2-((1R,3R)-3-((2S,3S)-2-amino-N,3-dimethyl-pentanamido)-4-methyl-1-propoxypentyl)thiazole-4-carboxamido)-2-methyl-5-phenylpentanoate(35): Fmoc-Ile-TuvOPr-Tup intermediate 32 (9 mg, 10 μmol) wasdeprotected as described above to provide 7 mg (quant.) of the titlecompound. UPLC-MS (system 2): t_(r)=1.29 min, m/z (ES+) calculated643.39 (M+H)⁺. found 643.55.

General procedure for the amide coupling ofisoleucine-tubuvaline(ether)-tubuphenylalanine tripeptides with(R)—N-methyl-pipecolic acid. Commercially available(R)—N-methyl-pipecolic acid (D-Mep) 36 (1.5-2 equivalents) was dissolvedin anhydrous dimethylformamide (25-50 mM) and pre-activated with HATU (2equivalents) and DIPEA (4 equivalents); the mixture was stirred for 10minutes at room temperature under nitrogen. The activated acid was thenadded to the Ile-Tuv(O-ether)-Tup tripeptides 33-35; the reaction wasstirred at room temperature under nitrogen and monitored by UPLC/MS.Upon reaction completion, glacial acetic acid (14 equivalents) was thenadded and the product was purified by preparative HPLC.

(2S,4R)-allyl4-(2-((1R,3R)-3-((2S,3S)—N,3-dimethyl-2-((R)-1-methylpiperidine-2-carboxamido)pentanamido)-1-methoxy-4-methylpentyl)thiazole-4-carboxamido)-2-methyl-5-phenylpentanoate(37): Ile-TuvOMe-Tup intermediate 33 (20 mg, 33 μmol) was coupled toD-Mep 36 as described above to provide 17 mg (71%) of the titlecompound. UPLC-MS (system 1): 1, =1.29 min, m/z (ES+) calculated 762.42(M+Na)⁺, found 762.32.

(2S,4R)-allyl4-(2-((1R,3R)-3-((2S,3S)—N,3-dimethyl-2-((R)-1-methylpiperidine-2-carboxamido)pentanamido)-1-ethoxy-4-methylpentyl)thiazole-4-carboxamido)-2-methyl-5-phenylpentanoate(38): Ile-TuvOEt-Tup intermediate 34 (20 mg, 33 μmol) was coupled toD-Mep 36 as described above to provide 17 mg (71%) of the titlecompound. UPLC-MS (system 2): t_(r)=1.25 min, m/z (ES+) calculated754.46 (M+H)⁺, found 754.55.

(2S,4R)-allyl4-(2-((1R,3R)-3-((2S,3S)—N,3-dimethyl-2-((R)-1-methylpiperidine-2-carboxamido)pentanamido)-4-methyl-1-propoxypentyl)thiazole-4-carboxamido)-2-methyl-5-phenylpentanoate(39): Ile-TuvOPr-Tup intermediate 35 (7 mg, 11 μmol) was coupled toD-Mep 36 as described above to provide 4.5 mg (53%) of the titlecompound. UPLC-MS (system 2): t_(r)=1.36 min, m/z (ES+) calculated768.48 (M+H)⁺, found 768.55.

General procedure for the allyl ester removal from D-methylpipecolicacid-isoleucine-tubuvaline(ether)-tubuphenylalanine tubulysinintermediates. Allyl ester-protected tubulysin ether intermediate(37-39) was dissolved in anhydrous dichloromethane (20 mM) treated withpalladium tetrakis(triphenylphosphine) (0.1 equiv.), triphenylphosphine(0.2 equivalents), and anhydrous pyrrolidine (8 equivalents), and thereaction was stirred at an ambient temperature under nitrogen. OnceUPLC/MS revealed conversion to the product free acid, the reaction wasquenched with glacial acetic acid (22 equivalents), diluted withacetonitrile and dimethylformamide, and then concentrated by rotaryevaporation. The crude tubulysin ether was then purified by preparativeHPLC.

(2S,4R)-4-(2-((1R,3R)-3-((2S,3S)—N,3-dimethyl-2-((R)-1-methylpiperidine-2-carboxamido)pentanamido)-1-methoxy-4-methylpentyl)thiazole-4-carboxamido)-2-methyl-5-phenylpentanoicacid (40): Allyl ester-protected tubulysin methyl ether (TubOMe)intermediate 37 (2.9 mg, 4 μmol) was deprotected as described above toprovide 2.5 mg (93%) of tubulysin methyl ether 40 (TubOMe). UPLC-MS(system 2): t_(r)=1.05 min, m/z (ES+) calculated 700.41 (M+H)⁺, found700.50.

(2S,4R)-4-(2-((1R,3R)-3-((2S,3S)—N,3-dimethyl-2-((R)-1-methylpiperidine-2-carboxamido)pentanamido)-1-ethoxy-4-methylpentyl)thiazole-4-carboxamido)-2-methyl-5-phenylpentanoicacid (41): Allyl ester-protected tubulysin ethyl ether (TubOEt)intermediate 38 (2.9 mg, 4 μmol) was deprotected as described above toprovide 2.5 mg (93%) of tubulysin ethyl ether 41 (TubOEt). UPLC-MS(system 2): t_(r)=1.09 min, m/z (ES+) calculated 714.43 (M+H)⁺, found714.51.

(2S,4R)-4-(2-((1R,3R)-3-((2S,3S)—N,3-dimethyl-2-((R)-1-methylpiperidine-2-carboxamido)pentanamido)-4-methyl-1-propoxypentyl)thiazole-4-carboxamido)-2-methyl-5-phenylpentanoicadd (42): Allyl ester-protected tubulysin propyl ether (TubOPr)intermediate 39 (6 mg, 8 μmol) was deprotected as described above toprovide 6 mg (quant.) of tubulysin propyl ether 42 (TubOPr). UPLC-MS(system 2): t_(r)=1.19 min, m/z (ES+) calculated 728.44 (M+H)⁺, found728.54.

(S)-perfluorophenyl3-((tert-butoxycarbonyl)amino)-2-(2,5-dioxo-2,5-dihydro-1H-pyrrol-1-yl)propanoate(44). A flask charged with mDPR(Boc)-OH (Nature Biotech, 2014, 32,1059-1062) 43 (500 mg, 1.76 mmol), to which PFP—OH (324 mg, 1.76 mmol)was added a solution in DMF (8.8 mL) followed by1-Ethyl-3-(3-dimethylaminopropyl)carbodiimide (371 mg, 1.93 mmol) as asolid. The reaction was stirred for 1 hour at room temperature thenquenched with 50 mL saturated NH₄Cl in H₂O and 50 mL H₂O. The aqueouslayer was extracted with DCM twice, the organics were then washed withbrine, dried over NaSO₄, and condensed under reduced pressure to provide44 (589 mg, 74%). Analytical UPLC-MS (system 2): t_(r)=1.51 min, m/z(ES+) calculated 473.07 (M+Na)⁺, found 473.14.

(2S,3R,4S,5S,6S)-2-(2-(3-((((9H-fluoren-9-yl)methoxy)carbonyl)amino)propanamido)-4-(bromomethyl)phenoxy)-6-(methoxycarbonyl)tetrahydro-2H-pyran-3,4,5-triyltriacetate (46): A flame dried flask was charged with known(Bioconjugate Chem. 2006, 17, 831-840) glucuronide linker fragment (45,210 mg, 281 μmol) in 4.5 mL anhydrous THF The solution was stirred atroom temperature under N₂. Triphenylphosphine (111 mg, 421.5 μmol) andN-bromosuccinimide (75 mg, 421.5 μmol) were added sequentially and thesolution was stirred for 2 hours. The reaction was condensed underreduced pressure and purified over silica via a Biotage column(Hexanes/EtOAc, 30%-50%-70%) to provide 46 (222 mg, 97%). AnalyticalUPLC-MS (system 1): t_(r)=2.36 min, m/z (ES+) found 811.34.

General procedure for quaternization of Tub(OR)-OAllyl to Fmoc-Gluc-Br:A pressure vessel was charged with Tub(OR)-OAllyl (37-39, 1 equivalent)and brominated glucuronide linker fragment (46, 1.5 equivalents) inanhydrous 2-butanone (50 mM). The reaction vessel was flushed with N₂and sealed. The reaction was then stirred and heated to 60° C. for 18hours. The resulting mixture was cooled, condensed to residue underreduced pressure, then carried forward crude or taken up in minimal DMSOto be purified by preparative HPLC.

(2R)-1-(3-(3-((((9H-fluoren-9-yl)methoxy)carbonyl)amino)propanamido)-4-(((2S,3R,4S,5S,6S)-3,4,5-triacetoxy-6-(methoxycarbonyl)tetrahydro-2H-pyran-2-yl)oxy)benzyl)-2-(((2S,3S)-1-(((1R,3R)-1-(4-(((2R,4S)-5-(allyloxy)-4-methyl-5-oxo-1-phenylpentan-2-yl)carbamoyl)thiazol-2-yl)-1-methoxy-4-methylpentan-3-yl)(methyl)amino)-3-methyl-1-oxopentan-2-yl)carbamoyl)-1-methylpiperidin-1-ium(47). Tub(OMe)-OAllyl 37 (13 mg, 18 μmol) was quaternized as above withGlue-Br 46 (17 mg, 28 μmol) to be carried forward without furtherpurification. Analytical UPLC-MS (system 1): t_(r)=1.61 min, m/z (ES+)calculated 1470.68 (M)⁺. found 1471.68.

(2R)-1-(3-(3-((((9H-fluoren-9-yl)methoxy)carbonyl)amino)propanamido)-4-(((2S,3R,4S,5S,6S)-3,4,5-triacetoxy-6-(methoxycarbonyl)tetrahydro-2H-pyran-2-yl)oxy)benzyl)-2-(((2S,3S)-1-(((1R,3R)-1-(4-(((2R,4S)-5-(allyloxy)-4-methyl-5-oxo-1-phenylpentan-2-yl)carbamoyl)thiazol-2-yl)-1-ethoxy-4-methylpentan-3-yl)(methyl)amino)-3-methyl-1-oxopentan-2-yl)carbamoyl)-1-methylpiperidin-1-ium(48). Tub(OEt)-OAllyl 38 (148 mg, 196 μmol) was quaternized as abovewith Gluc-Br 46 (175 mg, 216 μmol) to be carried forward without furtherpurification. Analytical UPLC-MS (system 2): t_(r)=1.49 min, m/z (ES+)calculated 1484.69 (M)⁺, found 1484.84.

(2R)-1-(3-(3-((((9H-fluoren-9-yl)methoxy)carbonyl)amino)propanamido)-4-(((2S,3R,4S,5S,6S)-3,4,5-triacetoxy-6-(methoxycarbonyl)tetrahydro-2H-pyran-2-yl)oxy)benzyl)-2-(((2S,3S)-1-(((1R,3R)-1-(4-(((2R,4S)-5-(allyloxy)-4-methyl-5-oxo-1-phenylpentan-2-yl)carbamoyl)thiazol-2-yl)-4-methyl-1-propoxypentan-3-yl)(methyl)amino)-3-methyl-1-oxopentan-2-yl)carbamoyl)-1-methylpiperidin-1-ium(49). Tub(OPr)-OAllyl 39 (43 mg, 56 μmol) was quaternized as above withGlue-Br 46 (50 mg, 62 μmol) to provide 49 (68%) after preparative LC.Analytical UPLC-MS (system 2): t_(r)=1.47 min, m/z (ES+) calculated1498.71 (M)+, found 1498.85.

General procedure for global deprotection of Fmoc-GlucQ-Tub(OR)-OAllyl:A flask was charged with Fmoc-GlucQ-Tub(OR)-OAllyl (47-49) in THF andMeOH and cooled to 0° C. LiOH.H₂O (6.0 equivalents) in H₂O was addeddropwise (1:1:1 THF:MeOH:H₂O, 50 mM end concentration) and the reactionwas allowed to warm to room temperature and stir overnight. THF and MeOHwere removed under reduced pressure, the resulting precipitate wasresolubilized using minimal DMSO and the mixture was purified bypreparative HPLC.

(2R)-1-(3-(3-aminopropanamido)-4-(((2S,3R,4S,5S,6S)-6-carboxy-3,4,5-trihydroxytetrahydro-2H-pyran-2-yl)oxy)benzyl)-2-(((2S,3S)-1-(((1R,3R)-1-(4-(((2R,4S)-4-carboxy-1-phenylpentan-2-yl)carbamoyl)thiazol-2-yl)-1-methoxy-4-methylpentan-3-yl)(methyl)amino)-3-methyl-1-oxopentan-2-yl)carbamoyl)-1-methylpiperidin-1-ium(50). Fmoc-GlucQ-Tub(OMe)-OAllyl 47 (17 mg, 12 μmol) was deprotected asabove to provide 50 (4.3 mg, 34%). Analytical UPLC-MS (system 1):t_(r)=1.08 min, m/z (ES+) calculated 1068.53 (M)+, found 1068.66.

(2R)-1-(3-(3-aminopropanamido)-4-(((2S,3R,4S,5S,6S)-6-carboxy-3,4,5-trihydroxytetrahydro-2H-pyran-2-yl)oxy)benzyl)-2-(((2S,3S)-1-((1R,3R)-1-(4-(((2R,4S)-4-carboxy-1-phenylpentan-2-yl)carbamoyl)thiazol-2-yl)-1-ethoxy-4-methylpentan-3-yl)(methyl)amino)-3-methyl-1-oxopentan-2-yl)carbamoyl)-1-methylpiperidin-1-ium(51). Fmoc-GlucQ-Tub(OEt)-OAllyl 48 (292 mg, 197 μmol) was deprotectedas above to provide 51 (116 mg, 54%). Analytical UPLC-MS (system 2):t_(r)=0.95 min, m/z (ES+) calculated 1082.55 (M)⁺, found 1082.68.

(2R)-1-(3-(3-aminopropanamido)-4-(((2S,3R,4S,5S,6S)-6-carboxy-3,4,5-trihydroxytetrahydro-2H-pyran-2-yl)oxy)benzyl)-2-(((2S,3S)-1-(((1R,3R)-1-(4-(((2R,4S)-4-carboxy-1-phenylpentan-2-yl)carbamoyl)thiazol-2-yl)-4-methyl-1-propoxypentan-3-yl)(methyl)amino)-3-methyl-1-oxopentan-2-yl)carbamoyl)-1-methylpiperidin-1-ium(52). Fmoc-GlucQ-Tub(OPr)-OAllyl 49 (57 mg, 38 μmol) was deprotected asabove to provide 52 (34 mg, 41%). Analytical UPLC-MS (system 2):t_(r)=0.98 min, m/z (ES+) calculated 1096.56 (M)⁺, found 1096.67.

General procedure for coupling of H-GlucQ-Tub(OR) to mDPR-OPFP: A flaskwas charged with H-Gluc-Tub(OR) (50-52) to which mDPR(Boc)-OPFP (44, 1.2equivalents) was added as a solution in DMF (10 mM).N,N-Diisopropylethylamine (4.0 equivalents) was added and the reactionwas stirred at room temperature for 3 hours. The reaction was quenchedwith AcOH (4.0 equivalents) then diluted in DMSO (1 volume) and purifiedby preparative HPLC.

(2R)-1-(3-(3-((S)-3-((tert-butoxycarbonyl)amino)-2-(2,5-dioxo-2,5-dihydro-1H-pyrrol-1-yl)propanamido)propanamido)-4-(((2S3R,4S,5S,6S)-6-carboxy-3,4,5-trihydroxytetrahydro-2H-pyran-2-yl)oxy)benzyl)-2-(((2S,3S)-1-(((1R,3R)-1-(4-(((2R,4S)-4-carboxy-1-phenylpentan-2-yl)carbamoyl)thiazol-2-yl)-1-methoxy-4-methylpentan-3-yl)(methyl)amino)-3-methyl-1-oxopentan-2-yl)carbamoyl)-1-methylpiperidin-1-ium(53). H-GlucQ-Tub(OMe) 50 (4.3 mg, 4 μmol) was coupled to mDPR-OPFP 44(2.2 mg, 4.8 μmol) as above to provide 53 (4 mg, 75%). AnalyticalUPLC-MS (system 1): t_(r)=1.22 min, m/z (ES+) calculated 1334.62 (M)⁺,found 1334.68.

(2R)-1-(3-(3-((S)-3-((tert-butoxycarbonyl)amino)-2-(2,5-dioxo-2,5-dihydro-1H-pyrrol-1-yl)propanamido)propanamido)-4-(((2S,3R,4S,5S,6S)-6-carboxy-3,4,5-trihydroxytetrahydro-2H-pyran-2-yl)oxy)benzyl)-2-(((2S,3S)-1-(((1R,3R)-1-(4-(((2R,4S)-4-carboxy-1-phenylpentan-2-yl)carbamoyl)thiazol-2-yl)-1-ethoxy-4-methylpentan-3-yl)(methyl)amino)-3-methyl-1-oxopentan-2-yl)carbamoyl)-1-methylpiperidin-1-ium(54). H-GlucQ-Tub(OEt) 51 (29 mg, 27 μmol was coupled to mDPR-OPFP 44(14 mg, 32 μmol as above to provide 54 (26 mg, 72%). Analytical UPLC-MS(system 2): t_(r)=1.19 min, m/z (ES+) calculated 1348.64 (M)⁺, found1348.79.

(2R)-1-(3-(3-((S)-3-((tert-butoxycarbonyl)amino)-2-(2,5-dioxo-2,5-dihydro-1H-pyrrol-1-yl)propanamido)propanamido)-4-(((2S,3R,4S,5S,6S)-6-carboxy-3,4,5-trihydroxytetrahydro-2H-pyran-2-yl)oxy)benzyl)-2-(((2S,3S)-1-(((1R,3R)-1-(4-(((2R,4S)-4-carboxy-1-phenylpentan-2-yl)carbamoyl)thiazol-2-yl)-4-methyl-1-propoxypentan-3-yl)(methyl)amino)-3-methyl-1-oxopentan-2-yl)carbamoyl)-1-methylpiperidin-1-ium(55). H-GlucQ-Tub(OPr) 52 (6 mg, 5 μmol) was coupled to mDPR-OPFP 44 (3mg, 6 μmol) as above to provide 55 (6 mg, 84%). Analytical UPLC-MS(system 2): t_(r)=1.24 min, m/z (ES+) calculated 1362.65 (M)⁺, found1362.78.

General procedure for deprotection of mDPR(Boc)-GlucQ-Tub(OR): A flaskwas charged with mDPR(Boc)-GlucQ-Tub(OR) (53-55) and cooled to 0° C. A10% solution of TFA in DCM (50 mM) was added and the reaction wasallowed to warm to room temperature while stirring for 1 hour. Thereaction was then diluted with DMSO (1 volume), DCM removed via reducedpressure, then purified by preparative HPLC.

(2R)-1-(3-(3-((S)-3-amino-2-(2,5-dioxo-2,5-dihydro-1H-pyrrol-1-yl)propanamido)propanamido)-4-(((2S,3R,4S,5S,6S)-6-carboxy-3,4,5-trihydroxytetrahydro-2H-pyran-2-yl)oxy)benzyl)-2-(((2S,3S)-1-(((1R,3R)-1-(4-(((2R,4S)-4-carboxy-1-phenylpentan-2-yl)carbamoyl)thiazol-2-yl)-1-methoxy-4-methylpentan-3-yl)(methyl)amino)-3-methyl-1-oxopentan-2-yl)carbamoyl)-1-methylpiperidin-1-ium(56). mDPR(Boc)-GlucQ-Tub(OMe) 53 (4 mg, 3 μmol) was deprotected asabove to provide 56 (2 mg, 54%). Analytical UPLC-MS (system 2):t_(r)=1.09 min, m/z (ES+) calculated 1234.57 (M)⁺, found 1234.65.

(2R)-1-(3-(3-((S)-3-amino-2-(2,5-dioxo-2,5-dihydro-1H-pyrrol-1-yl)propanamido)propanamido)-4-(((2S,3R,4S,5S,6S)-6-carboxy-3,4,5-trihydroxytetrahydro-2H-pyran-2-yl)oxy)benzyl)-2-(((2S,3S)-1-(((1R,3R)-1-(4-(((2R,4S)-4-carboxy-1-phenylpentan-2-yl)carbamoyl)thiazol-2-yl)-1-ethoxy-4-methylpentan-3-yl)(methyl)amino)-3-methyl-1-oxopentan-2-yl)carbamoyl)-1-methylpiperidin-1-ium(57). mDPR(Boc)-GlucQ-Tub(OEt) 54 (26 mg, 19 μmol) was deprotected asabove to provide 57 (24 mg, 99%). Analytical UPLC-MS (system 2):t_(r)=0.95 min, n/7 (ES+) calculated 1248.59 (M)⁺, found 1248.72.

(2R)-1-(3-(3-((S)-3-amino-2-(2,5-dioxo-2,5-dihydro-1H-pyrrol-1-yl)propanamido)propanamido)-4-(((2S,3R,4S,5S,6S)-6-carboxy-3,4,5-trihydroxytetrahydro-2H-pyran-2-yl)oxy)benzyl)-2-(((2S,3S)-1-((1R,3R)-1-(4-(((2R,4S)-4-carboxy-1-phenylpentan-2-yl)carbamoyl)thiazol-2-yl)-4-methyl-1-propoxypentan-3-yl)(methyl)amino)-3-methyl-1-oxopentan-2-yl)carbamoyl)-1-methylpiperidin-1-ium(58). mDPR(Boc)-GlucQ-Tub(OPr) 55 (6 mg, 4 μmol) was deprotected asabove to provide 58 (4 mg, 75%). Analytical UPLC-MS (system 2):t_(r)=1.03 min, m/z (ES+) calculated 1262.60 (M)⁺, found 1262.73.

General procedure for coupling of H-GlucQ-Tub(OR) to Fmoc-LysPEG12)-OSu:A was flask charged with H-GlucQ-Tub(OR) (51 or 52), to whichFmoc-Lys(PEG12)-OSu (WO 2015057699) (1.2 equivalents) was added asolution in DMF (20 mM) followed by N,N-Diisopropylethylamine (4.0equivalents). The reaction was stirred at room temperature for 4 hoursthen quenched with AcOH (4.0 equivalents), diluted in DMSO (1 volume)and purified by preparative HPLC.

(2R)-1-(3-((S)-44-((((9H-fluoren-9-yl)methoxy)carbonyl)amino)-38,45-dioxo-2,5,8,11,14,17,20,23,26,29,32,35-dodecaoxa-39,46-diazanonatetracontanamido)-4-(((2S,3R,4S,5S,6S)-6-carboxy-3,4,5-trihydroxytetrahydro-2H-pyran-2-yl)oxy)benzyl)-2-(((2S,3S)-1-(((1R,3R)-1-(4-(((2R,4S)-4-carboxy-1-phenylpentan-2-yl)carbamoyl)thiazol-2-yl)-1-ethoxy-4-methylpentan-3-yl)(methyl)amino)-3-methyl-1-oxopentan-2-yl)carbamoyl)-1-methylpiperidin-1-ium(60). H-GlucQ-Tub(OEt) 51 (87 mg, 80 μmol) was coupled toFmoc-Lys(PEG12)-OSu 59 (100 mg, 96 μmol) as above to provide 60 (108 mg,67%). Analytical UPLC-MS (system 2): t_(r)=1.29 min, m/z (ES+)calculated 2003.04 (M)⁺, found 2003.24.

(2R)-1-(3-((S)-44-((((9H-fluoren-9-yl)methoxy)carbonyl)amino)-38,45-dioxo-2,5,8,11,14,17,20,23,26,29,32,35-dodecaoxa-39,46-diazanonatetracontanamido)-4-(((2S,3R,4S,5S,6S)-6-carboxy-3,4,5-trihydroxytetrahydro-2H-pyran-2-yl)oxy)benzyl)-2-(((2S,3S)-1-(((1R,3R)-1-(4-(((2R,4S)-4-carboxy-1-phenylpentan-2-yl)carbamoyl)thiazol-2-yl)-4-methyl-1-propoxypentan-3-yl)(methyl)amino)-3-methyl-1-oxopentan-2-yl)carbamoyl)-1-methylpiperidin-1-ium(61). H-GlucQ-Tub(OPr) 52 (20 mg, 18 μmol) was coupled toFmoc-Lys(PEG12)-OSu 59 (23 mg, 22 μmol) as above to provide 61 (27 mg,73%). Analytical UPLC-MS (system 2): t_(r)=1.31 min, m/z (ES+)calculated 2017.05 (M)⁺, found 2017.22.

General procedure deprotection of Fmoc-Lys(PEG12)-GlucQ-Tub(OR): A flaskwas charged with Fmoc-Lys(PEG12)-GlucQ-Tub(OR) (60 or 61), to which a20% solution of piperidine in DMF (20 mM) was added. The reaction wasstirred for 30 minutes then diluted in DMSO (1 volume) and purified bypreparative HPLC.

(2R)-1-(3-((S)-44-amino-38,45-dioxo-2,5,8,11,14,17,20,23,26,29,32,35-dodecaoxa-39,46-diazanonatetracontanamido)-4-(((2S,3R,4S,5S,6S)-6-carboxy-3,4,5-trihydroxytetrahydro-2H-pyran-2-yl)oxy)benzyl)-2-(((2S,3S)-1-(((1R,3R)-1-(4-(((2R,4S)-4-carboxy-1-phenylpentan-2-yl)carbamoyl)thiazol-2-yl)-1-ethoxy-4-methylpentan-3-yl)(methyl)amino)-3-methyl-1-oxopentan-2-yl)carbamoyl)-1-methylpiperidin-1-ium(62). Fmoc-Lys(PEG12)-GlucQ-Tub(OEt) 60 (108 mg, 54 μmol) wasdeprotected as above to provide 62 (83 mg, 86%). Analytical UPLC-MS(system 2): t, =0.99 min, m/z (ES+) calculated 1780.97 (M)⁺, found1781.14.

(2R)-1-(3-((S)-44-amino-38,45-dioxo-2,5,8,11,14,17,20,23,26,29,32,35-dodecaoxa-39,46-diazanonatetracontanamido)-4-(((2S,3R,4S,5S,6S)-6-carboxy-3,4,5-trihydroxytetrahydro-2H-pyran-2-yl)oxy)benzyl)-2-(((2S,3S)-1-(((1R,3R)-1-(4-(((2R,4S)-4-carboxy-1-phenylpentan-2-yl)carbamoyl)thiazol-2-yl)-4-methyl-1-propoxypentan-3-yl)(methyl)amino)-3-methyl-1-oxopentan-2-yl)carbamoyl)-1-methylpiperidin-1-ium(63). Fmoc-Lys(PEG12)-GlucQ-Tub(OPr) 61 (27 mg, 13 μmol) was deprotectedas above to provide 63 (17 mg, 71%). Analytical UPLC-MS (system 2): t,=1.03 min, m/z (ES+) calculated 1794.98 (M)⁺, found 1795.14.

General procedure for coupling H-Lys(PEG12)-GlucQ-Tub(OR) to mDPR-OPFP:A flask was charged with H-Lys(PEG12)-GlucQ-Tub(OR) (62 or 63), to whichmDPR-OPFP (44, 1.2 equivalents) was added as a solution in DMF (10 mM)followed by N,N-Diisopropylethylamine (4.0 equivalents). The reactionwas stirred at room temperature for 4 hours then quenched with AcOH (4.0equivalents), diluted in DMSO (1 volume) and purified by preparativeHPLC.

(2R)-1-(3-((S)-44-((S)-3-((tert-butoxycarbonyl)amino)-2-(2,5-dioxo-2,5-dihydro-1H-pyrrol-1-yl)propanamido)-38,45-dioxo-2,5,8,11,14,17,20,23,26,29,32,35-dodecaoxa-39,46-diazanonatetracontanamido)-4-(((2S,3R,4S,5S,6S)-6-carboxy-3,4,5-trihydroxytetrahydro-2H-pyran-2-yl)oxy)benzyl)-2-(((2S,3S)-1-(((1R,3R)-1(4-(((2R,4S)-4-carboxy-1-phenylpentan-2-yl)carbamoyl)thiazol-2-yl)-1-ethoxy-4-methylpentan-3-yl)(methyl)amino)-3-methyl-1-oxopentan-2-yl)carbamoyl)-1-methylpiperidin-1-ium(64). H-Lys(PEG12)-GlucQ-Tub(OEt) (83 mg, 46 μmol) was coupled tomDPR-OPFP 44 (25 mg, 56 μmol) as above to provide 64 (43 mg, 45%).Analytical UPLC-MS (system 2): t_(r)=1.22 min, m/z (ES+) calculated2047.06 (M)⁺, found 2047.25.

(2R)-1-(3-((S)-44-((S)-3-((tert-butoxycarbonyl)amino)-2-(2,5-dioxo-2,5-dihydro-1H-pyrrol-1-yl)propanamido)-38,45-dioxo-2,5,8,11,14,17,20,23,26,29,32,35-dodecaoxa-39,46-diazanonatetracontanamido)-4-(((2S,3R,4S,5S,6S)-6-carboxy-3,4,5-trihydroxytetrahydro-2H-pyran-2-yl)oxy)benzyl)-2-(((2S,3S)-1-(((1R,3R)-1-(4-(((2R,4S)-4-carboxy-1-phenylpentan-2-yl)carbamoyl)thiazol-2-yl)-4-methyl-1-propoxypentan-3-yl)(methyl)amino)-3-methyl-1-oxopentan-2-yl)carbamoyl)-1-methylpiperidin-1-ium(65). H-Lys(PEG12)-GlucQ-Tub(OPr) (17 mg, 9 μmol) was coupled tomDPR-OPFP 44 (5 mg, 11 μmol) as above to provide 65 (14 mg, 74%).Analytical UPLC-MS (system 2): t_(r)=1.22 min. m/z (ES+) calculated2061.07 (M)⁺, found 2061.26.

General procedure for deprotection ofmDPR(Boc)-Lys(PEG12)-GlucQ-Tub(OR): A flask was charged withmDPR(Boc)-Lys(PEG12)-GlucQ-Tub(OR) (64 or 65) and cooled to 1° C. A 10%solution of TFA in DCM (50 mM) was added and the reaction was allowed towarm to room temperature while stirring for 1 hour. The reaction wasthen diluted with DMSO (0 volume), DCM removed via reduced pressure,then purified by preparative HPLC.

(2R)-1-(3-((S)-44-((S)-3-amino-2-(2,5-dioxo-2,5-dihydro-1H-pyrrol-1-yl)propanamido)-38,45-dioxo-2,5,8,11,14,17,20,23,26,29,32,35-dodecaoxa-39,46-diazanonatetracontanamido)-4-(((2S,3R,4S,5S,6S)-6-carboxy-3,4,5-trihydroxytetrahydro-2H-pyran-2-yl)oxy)benzyl)-2-(((2S,3S)-1-(((1R,3R)-1-(4-(((2R,4S)-4-carboxy-1-phenylpentan-2-yl)carbamoyl)thiazol-2-yl)-1-ethoxy-4-methylpentan-3-yl)(methyl)amino)-3-methyl-1-oxopentan-2-yl)carbamoyl)-1-methylpiperidin-1-ium(66). mDPR(Boc)-Lys(PEG12)-GlucQ-Tub(OEt) 64 (43 mg, 21 μmol) wasdeprotected as above to provide 66 (34 mg, 83%). Analytical UPLC-MS(system 2): t_(r)=0.96 min, m/z (ES+) calculated 1947.01 (M)⁺, found1947.22.

(2R)-1-(3-((S)-44-((S)-3-amino-2-(2,5-dioxo-2,5-dihydro-1H-pyrrol-1-yl)propanamido)-38,45-dioxo-2,5,8,11,14,17,20,23,26,29,32,35-dodecaoxa-39,46-diazanonatetracontanamido)-4-(((2S,3R,4S,5S,6S)-6-carboxy-3,4,5-trihydroxytetrahydro-2H-pyran-2-yl)oxy)benzyl)-2-(((2S,3S)-1-(((1R,3R)-1(4-(((2R,4S)-4-carboxy-1-phenylpentan-2-yl)carbamoyl)thiazol-2-yl)-4-methyl-1-propoxypentan-3-yl)(methyl)amino)-3-methyl-1-oxopentan-2-yl)carbamoyl)-1-methylpiperidin-1-ium(67). mDPR(Boc)-Lys(PEG12)-GlucQ-Tub(OPr) 65 (14 mg, 7 μmol) wasdeprotected as above to provide 67 (12 mg, 92%). Analytical UPLC-MS(system 2): t_(r)=1.05 min, m/z (ES+) calculated 1961.02 (M)⁺, found1961.20.

(2S,4R)-4-(2-((1R,3R)-3-((tert-butoxycarbonyl)(methyl)amino)-1-hydroxy-4-methylpentyl)thiazole-4-carboxamido)-2-methyl-5-phenylpentanoicacid (69). A flask was charged with commercially availableBoc-Tuv(OAc)-Tup-OEt (68, 50 mg, 81 μmol) in THF (1.35 mL) and MeOH(1.35 mL) and cooled to 0° C. LiOH H₂O (27 mg, 647 μmol) was solubilizedin H₂O (1.35 mL) then added dropwise. The reaction was allowed to warmto room temperature and stirred for 3 hours. The reaction was thenquenched with acetic acid (37 μL, 647 μmol) and condensed under reducedpressure. The residue was taken up in minimal DMSO and purified bypreparative HPLC to provide 69 (44 mg, quant.). Analytical UPLC-MS(system 2): t_(r)=1.53 min, m/z (ES+) calculated 548.28 (M+H)⁺, found548.24.

(2S,4R)-allyl4-(2-((1R,3R)-1-acetoxy-3-((tert-butoxycarbonyl)(methyl)amino)-4-methylpentyl)thiazole-4-carboxamido)-2-methyl-5-phenylpentanoate(70). Boc-Tuv(OH)-Tup-OH (69.44 mg, 81 μmol) was solubilized inanhydrous pyridine (1.6 mL) and stirred at room temperature under N₂.Acetic anhydride (15.4 IL, 162 μmol) was added dropwise. 1.0 additionalequivalent of acetic anhydride was added after one hour of stirring andthe reaction was complete by LCMS after 2 hours. The reaction wasconcentrated to dryness under reduced pressure then resolubilized inanhydrous allyl alcohol (1.6 mL). Diallyl pyrocarbonate (54 μL, 325μmol) was added Followed by solid DMAP (3.0 mg, 24 μmol). The reactionwas allowed to stir at room temperature and monitored by LCMS,additional diallyl pyrocarbonate added as needed to push reaction tocompletion (4.0 additional equivalents). The reaction was then taken upin DMSO, condensed under reduced pressure, and purified by preparativeHPLC to provide 70 (33 mg, 65%). Analytical UPLC-MS (system 2):t_(r)=1.75 min, m/z (ES+) calculated 630.32 (M+H)⁺, found 630.42.

(2S,4R)-allyl4-(2-((1R,3R)-1-acetoxy-4-methyl-3-(methylamino)pentyl)thiazole-4-carboxamido)-2-methyl-5-phenylpentanoate(71). A flask charged with Boc-Tuv(OAc)-Tup-OEt (70, 33 mg, 21 μmol) wascooled to 0° C. under N₂. A solution of 10% TFA in CH₂Cl₂ (0.52 mL) wasadded dropwise and stirred for 4 hours. The reaction was concentratedunder reduced pressure, resolubilized in DCM, and condensed 3 times toremove TFA then carried forward without further purification. AnalyticalUPLC-MS (system 2): t_(r)=1.03 min, m/z (ES+) calculated 530.27 (M+H)⁺,found 530.36.

(2S,4R)-allyl4-(2-((6S,9R,11R)-6-((S)-sec-butyl)-9-isopropyl-2,2,8-trimethyl-4,7,13-trioxo-3,12-dioxa-5,8-diazatetradecan-11-yl)thiazole-4-carboxamido)-2-methyl-5-phenylpentanoate(72). To a flask charged with H-Tuv(OAc)-Tup-OAllyl (71, 28 mg, 53 μmol)was added Boc-L-Ile-OH (15 mg, 63 μmol) and HATU (40 mg, 106 μmol) assolids followed by DMF (1.0 mL). N,N-Diisopropylethylamine (37 μL, 211μmol) was added and the reaction was stirred at room temperature for 48hours. The reaction was then taken up in DMSO, condensed under reducedpressure, and purified by preparative HPLC to provide 72 (19 mg, 49%).Analytical UPLC-MS (system 2): t_(r)=1.72 min, m/z (ES+) calculated743.41 (M+H)⁺, found 743.51.

(2S,4R)-allyl4-(2-((1R,3R)-1-acetoxy-3-((2S,3S)-2-amino-N,3-dimethylpentanamido)-4-methylpentyl)thiazole-4-carboxamido)-2-methyl-5-phenylpentanoate(73). A flask charged with Boc-Ile-Tuv(OAc)-Tup-OEt (72, 19 mg, 26 μmol)was cooled to 0° C. under N₂. A solution of 10% TFA in CH₂Cl₂ (0.52 mL)was added dropwise and stirred for 4 hours. The reaction wasconcentrated under reduced pressure, resolubilized in DCM, and condensed3 times to remove TFA then carried forward without further purification.Analytical UPLC-MS (system 2): t_(r)=1.18 min, m/z (ES+) calculated643.36 (M+H)⁺, found 643.42.

(R)-tert-butyl 1-methylpiperidine-2-carboxylate (75). Commerciallyavailable H-Pip-OtBu (74, 500 mg, 2.70 mmol) was taken up in MeOH (4.50mL), AcOH (4.50 mL) and 37% CH₂O in H₂O (4.50 mL) and stirred for 20minutes. NaBH₃CN (509 mg, 8.10 mmol) added slowly as a solid to vigorousbubbling, stir for 30 minutes. The reaction was then poured into 200 mLsaturated NaHCO₃ solution and extracted 3× with 200 mL DCM. The organiclayers were washed with brine, dried over NaSO₄, and condensed underreduced pressure to provide 75 (516 mg, 96%) to be carried forwardwithout further purification. Analytical UPLC-MS (system 2): t_(r)=0.53min, m/z (ES+9) calculated 200.17 (M+H)⁺, found 200.21.

(2R)-1-(3-(3-((((9H-fluoren-9-yl)methoxy)carbonyl)amino)propanamido)-4-(((2S,3R,4S,5S,6S)-3,4,5-triacetoxy-6-(methoxycarbonyl)tetrahydro-2H-pyran-2-yl)oxy)benzyl)-2-(tert-butoxycarbonyl)-1-methylpiperidin-1-ium(76). A pressure vessel was charged with brominated glucuronide linkerfragment (46, 104 ag, 128 mol) and Mep-OtBu (75, 34 mg, 171 μmol) inanhydrous 2-butanone (1.71 mL). The reaction vessel was flushed with N₂and sealed. The reaction was then stirred and heated to 60° C. for 12hours. The resulting mixture was cooled, condensed under reducedpressure, taken up in minimal DMSO and purified by preparative HPLC toprovide 76 (97 mg, 82%). Analytical UPLC-MS (system 2): t_(r)=1.32 min,m/z (ES+) calculated 930.40 (M)⁺, found 930.49.

(2R)-1-(3-(3-((((9H-fluoren-9-yl)methoxy)carbonyl)amino)propanamido)-4-(((2S,3R,4S,5S,6S)-6-((allyloxy)carbonyl)-3,4,5-trihydroxytetrahydro-2H-pyran-2-yl)oxy)benzyl)-2-(tert-butoxycarbonyl)-1-methylpiperidin-1-ium(77). A flame dried flask was charged with Fmoc-GlucQ-Mep-OtBu (76.97mg, 104 μmol) in anhydrous allyl alcohol (2.09 mL) under N₂. Ti(OC₂H₅)₄(87 μL, 417 μmol) was added and the reaction was heated to 80° C. withstirring for 2 hours. The reaction was then cooled to room temperatureand poured into 50 mL 1M HCL. After resting for 45m, the HCl wasextracted 3× with 50 mL DCM. Resulting organics were washed with brine,dried over NaSO₄, condensed, and purified by preparative HPLC to provide77 (42 mg, 48%). Analytical UPLC-MS (system 2): t_(r)=1.18 min, m/z(ES+) calculated 830.39 (M)⁺, found 830.49.

(2R)-1-(3-(3-((((9H-fluoren-9-yl)methoxy)carbonyl)amino)propanamido)-4-(((2S,3R,4S,5S,6S)-6-((allyloxy)carbonyl)-3,4,5-trihydroxytetrahydro-2H-pyran-2-yl)oxy)benzyl)-2-carboxy-1-methylpiperidin-1-ium(78). A flask containing Fmoc-Gluc(Allyl)Q-Mep-OtBu (77, 42 mg, 50 μmol)was cooled to 0° C. under N₂. A solution of 30% TFA in CH₂Cl₂ (2.5 mL)was added dropwise and stirred for 18 hours. The reaction wasconcentrated under reduced pressure, taken up in minimal DMSO andpurified by preparative HPLC to provide 78 (25 mg, 64%). AnalyticalUPLC-MS (system 2): t_(r)=1.05 min, m/z (ES+) calculated 774.32 (M)⁺,found 774.42.

(2R)-1-(3-(3-((((9H-fluoren-9-yl)methoxy)carbonyl)amino)propanamido)-4-(((2S,3R,4S,5S,6S)-6-((allyloxy)carbonyl)-3,4,5-trihydroxytetrahydro-2H-pyran-2-yl)oxy)benzyl)-2-(((2S,3S)-1-(((1R,3R)-1-acetoxy-1-(4-(((2R,4S)-5-(allyloxy)-4-methyl-5-oxo-1-phenylpentan-2-yl)carbamoyl)thiazol-2-yl)-4-methylpentan-3-yl)(methyl)amino)-3-methyl-1-oxopentan-2-yl)carbamoyl)-1-methylpiperidin-1-ium(79). To a flask charged with H-Ile-Tuv(OAc)-Tup-OAllyl (73, 23 mg, 36μmol) was added Fmoc-Gluc(Allyl)Q-Mep-OH (78, 28 mg, 36 μmol) and HATU(27 mg, 72 μmol) as solids followed by DMF (0.714 mL).N,N-Diisopropylethylamine (25 μL, 143 μmol) was added and the reactionwas stirred at room temperature for 1 hour. The reaction was then takenup in DMSO and purified by preparative LC to provide 79 (23 mg, 46%).Analytical UPLC-MS (system 2): t_(r)=1.39 min, m/z (ES+) calculated1398.66 (M)⁺, found 1398.81.

(2R)-2-(((2S,3S)-1-(((1R,3R)-1-acetoxy-1-(4-(((2R,4S)-4-carboxy-1-phenylpentan-2-yl)carbamoyl)thiazol-2-yl)-4-methylpentan-3-yl)(methyl)amino)-3-methyl-1-oxopentan-2-yl)carbamoyl)-1-(3-(3-aminopropanamido)-4-(((2S,3R,4S,5S,6S)-6-carboxy-3,4,5-trihydroxytetrahydro-2H-pyran-2-yl)oxy)benzyl)-1-methylpiperidin-1-ium(80). Fmoc-Gluc(Allyl)Q-TubM-OAllyl (79, 21 mg, 15 μmol) was taken up inDCM (1.5 mL) stirring under N₂. Pd(PPh₃)₄ (3.5 mg, 3.1 μmol) and PPh₃(1.6 mg, 6.1 μmol were added as solids followed by pyrrolidine (20.1 μL,245 μmol). The reaction was stirred to 2 hours at room temperature thentaken up in 1 mL DMSO, condensed under reduced pressure, and purified bypreparative LC to provide 80 (13 mg, 79%). Analytical UPLC-MS (system2): t_(r)=0.94 min. m/z (ES+) calculated 1096.53 (M)⁺, found 1096.65.

(2R)-2-(((2S,3S)-1-(((1R,3R)-1-acetoxy-1-(4-(((2R,4S)-4-carboxy-1-phenylpentan-2-yl)carbamoyl)thiazol-2-yl)-4-methylpentan-3-yl)(methyl)amino)-3-methyl-1-oxopentan-2-yl)carbamoyl)-1-(3-(3-((S)-3-((tert-butoxycarbonyl)amino)-2-(2,5-dioxo-2,5-dihydro-1H-pyrrol-1-yl)propanamido)propanamido)-4-(((2S,3R,4S,5S,6S)-6-carboxy-3,4,5-trihydroxytetrahydro-2H-pyran-2-yl)oxy)benzyl)-1-methylpiperidin-1-ium(81). A flask was charged with H-GlucQ-TubM (80, 13.1 mg, 11.9 μmol) inanhydrous DMF (0.595 mL) to which mDPR(Boc)-OSu (13, 4.6 mg, 11.9 μmol)was added under N₂. N,N-Diisopropylethylamine (8.3 μL, 47.8 μmol) wasadded and the reaction was stirred at room temperature for 3 hours. Thereaction was then quenched with acetic acid (8.3 μL) and purified bypreparative HPLC to provide 81 (5.2 mg, 33%). Analytical UPLC-MS (system2): t_(r)=1.20 min, m/z (ES+) calculated 1362.62 (M)⁺, found 1362.75.

(2R)-2-(((2S,3S)-1-(((1R,3R)-1-acetoxy-1-(4-(((2R,4S)-4-carboxy-1-phenylpentan-2-yl)carbamoyl)thiazol-2-yl)-4-methylpentan-3-yl)(methyl)amino)-3-methyl-1-oxopentan-2-yl)carbamoyl)-1-(3-(3-((S)-3-amino-2-(2,5-dioxo-2,5-dihydro-1H-pyrrol-1-yl)propanamido)propanamido)-4-(((2S,3R,4S,5S,6S)-6-carboxy-3,4,5-trihydroxytetrahydro-2H-pyran-2-yl)oxy)benzyl)-1-methylpiperidin-1-ium(82). A flask charged with mDPR(Boc)-GlucQ-TubM (81, 5.2 mg, 3.8 μmol)was cooled to 0° C. under N₂. A solution of 10% TFA in CH₂Cl₂ (0.84 mL)was added dropwise and stirred for 4 hours. The reaction was then takenup in DMSO, condensed under reduced pressure, and purified bypreparative HPLC to provide 82 (4.8 mg, 81%). Analytical UPLC-MS (system2): t_(r)=0.95 min, m/z (ES+) calculated 1262.56 (M)⁺, found 1262.68.

(S)-tert-butyl4-amino-5-((4-(hydroxymethyl)phenyl)amino)-5-oxopentanoate (84). A flaskcharged with Fmoc-Glu(OtBu)-OH (83, 2.0 g, 4.7 mmol), H-PABA (4, 579 mg,4.7 mmol), and Cl₂CH₂ (25 mL) was stirred at room temperature. EEDQ(1.40 g, 5.6 mmol) was added as a solid and the mixture was stirredovernight. Product was eluted from a 4 mm chromatotron plate with EtOAc,product containing fractions were condensed. The resulting residue wastaken up in 20% piperidine in DCM, stirred for 15 minutes, thencondensed to an oil. The oil was dissolved in D -M and eluted from a 2mm chromatotron plate using 10%-20% MeOH in DCM gradient to provide 84(860 mg, 60%). Analytical UPLC-MS (system 2): t_(r)=0.65 min, m/z (ES+)calculated 309.18 (M+H)⁺, found 309.24.

(S)-tert-butyl4-((S)-2-((tert-butoxycarbonyl)amino)-3-methylbutanamido)-5-((4-(hydroxymethyl)phenyl)amino)-5-oxopentanoate(85). To a flask charged with H-Glu(OtBu)-PABA (84, 860 mg, 2.78 mmol)in DMF (10 mL) was added Boc-Val-OSu 1 (1.13 g, 3.60 mmol) and DIPEA(0.75 mL). After 30 minutes the reaction mixture was poured into 100 mLEtOAc and washed with H₂O 3×, brine 1×, and dried over NaSO₄. Thesolution was dried under reduced pressure, solubilized in 50 mL EtOAc,and precipitated by 10% EtOAc in hexanes (50 mL). The solids werecollected and dried to provide 85 as a white solid (0.97 g, 70%).Analytical UPLC-MS (system 2): t_(r)=1.37 min, m/z (ES+) calculated508.30 (M+H)⁺, found 508.38.

(S)-tert-butyl5-((4-(bromomethyl)phenyl)amino)-4-((S)-2-((tert-butoxycarbonyl)amino)-3-methylbutanamido)-5-oxopentanoate(86). A flask charged with Boc-Val-Glu(OtBu)-PABA-OH (85, 200 mg, 394μmol), N-bromosuccinimide (105 mg, 591 μmol), and triphenylphosphine(155 mg, 591 μmol) was flushed with N₂. The reaction was taken up in THF(4 mL) and stirred for 12 hours. The reaction was condensed and purifiedover silica via a Biotage column (Hexanes/EtOAc, 10%-100%) to provide 86(210 mg, 93%). Analytical UPLC-MS (system 2): t_(r)=1.56 min, m/z (ES+)calculated 570.22 (M+H)⁺, found 570.30.

(2R)-2-(((2S,3S)-1-(((1R,3R)-1-acetoxy-1-(4-(((2R,4S)-5-(allyloxy)-4-methyl-5-oxo-1-phenylpentan-2-yl)carbamoyl)thiazol-2-yl)-4-methylpentan-3-yl)(methyl)amino)-3-methyl-1-oxopentan-2-yl)carbamoyl)-1-(4-((S)-5-(tert-butoxy)-2-((S)-2-((tert-butoxycarbonyl)amino)-3-methylbutanamido)-5-oxopentanamido)benzyl)-1-methylpiperidin-1-ium(88). A flask charged with Boc-Val-Glu(OtBu)-PABA-Br (86, 40 mg, 70μmol) and Tub-OAllyl (Org. Lett., 2007, 9, 1605-1607) (87, 45 mg, 59μmol) was flushed with N₂. Butanone (1.17 mL) was added and the reactionwas heated to 60° C. while stirring. After 18 hours the reaction wascondensed to dryness, taken up in minimal DCM, and purified via Biotage(0-20% DCM/MeOH) to provide 88 (62 mg, 85%). Analytical UPLC-MS (system2): t_(r)=1.47 min, m/z (ES+) calculated 1257.72 (M)⁺, found 1257.85.

(2R)-2-(((2S,3S)-1-(((1R,3R)-1-acetoxy-1-(4-(((2R,4S)-4-carboxy-1-phenylpentan-2-yl)carbamoyl)thiazol-2-yl)-4-methylpentan-3-yl)(methyl)amino)-3-methyl-1-oxopentan-2-yl)carbamoyl)-1-(4-((S)-2-((S)-2-amino-3-methylbutanamido)-4-carboxybutanamido)benzyl)-1-methylpiperidin-1-ium(89). A flask charged with Boc-Val-Glu(OtBu)-PABQ-Tub-OAllyl (88, 42 mg,50 μmol) was cooled to 0° C. under N₂. A solution of 30% TFA in CH₂Cl₂(0.99 mL) was added dropwise and stirred for 18 hours. The reaction wasconcentrated under reduced pressure, taken up in DCM and recondensed 3times. The residue was then taken up in DCM (0.98 mL) to which Pd(PPh₃)₄(5.7 mg, 4.9 μmol) and PPh₃ (2.6 mg, 9.8 μmol) were added as solidsfollowed by pyrrolidine (32 μL, 392 μmol). After 1 hour the reaction wastaken up in minimal DMSO, condensed, and purified by preparative HPLC toprovide 89 (47 mg, 90%). Analytical UPLC-MS (system 2): t_(r)=0.95 min,m/z (ES+) calculated 1061.57 (M)⁺, found 1061.69.

(2R)-2-(((2S,3S)-1-(((1R,3R)-1-acetoxy-1-(4-(((2R,4S)-4-carboxy-1-phenylpentan-2-yl)carbamoyl)thiazol-2-yl)-4-methylpentan-3-yl)(methyl)amino)-3-methyl-1-oxopentan-2-yl)carbamoyl)-1-(4-((7S,10S,13S)-13-(2-carboxyethyl)-7-(2,5-dioxo-2,5-dihydro-1H-pyrrol-1-yl)-10-isopropyl-2,2-dimethyl-4,8,11-trioxo-3-oxa-5,9,12-triazatetradecanamido)benzyl)-1-methylpiperidin-1-ium(90). A flask was charged with H-ValGluPABQ-Tub (89, 22.5 mg, 21.2 μmol)in anhydrous DMF (0.420 mL), to which mDPR(Boc)-OSu (13, 8.9 mg, 23.3μmol) was added as a solid under N₂. N,N-Diisopropylethylamine (14.8 μL,84.7 μmol) was added and the reaction was stirred at room temperaturefor 3 hours. The reaction was then quenched with acetic acid (14.8 μL)and purified by preparative HPLC to provide 90 (11.5 mg, 40%).Analytical UPLC-MS (system 2): t_(f)=1.31 min, m/z (ES+) calculated1327.66 (M)⁺. found 1327.94.

(2R)-2-(((2S,3S)-1-(((1R,3R)-1-acetoxy-1-(4-(((2R,4S)-4-carboxy-1-phenylpentan-2-yl)carbamoyl)thiazol-2-yl)-4-methylpentan-3-yl)(methyl)amino)-3-methyl-1-oxopentan-2-yl)carbamoyl)-1-(4-((S)-2-((S)-2-((S)-3-amino-24(2,5-dioxo-2,5-dihydro-1H-pyrrol-1-yl)propanamido)-3-methylbutanamido)-4-carboxybutanamido)benzyl)-1-methylpiperidin-1-ium(91). A flask charged with mDPR(Boc)-ValGluPABQ-Tub (90, 11.5 mg, 8.6μmol) was cooled to 0° C. under N₂. A solution of 10% TFA in CH₂Cl₂(0.86 mL) was added dropwise and stirred for 2 hours. The reaction wasthen taken up in DMSO, condensed under reduced pressure, and purified bypreparative HPLC to provide 91 (9.9 mg, 93%). Analytical UPLC-MS (system2): t_(r)=0.99 min, m/z (ES+) calculated 1227.61 (M)⁺, found 1227.83.

(2R)-1-(4-((44S,47S,50S)-44-((((9H-fluoren-9-yl)methoxy)carbonyl)amino)-50-(2-carboxyethyl)-47-isopropyl-38,45,48-trioxo-2,5,8,11,14,17,20,23,26,29,32,35-dodecaoxa-39,46,49-triazahenpentacontanamido)benzyl)-2-(((2S,3S)-1-(((1R,3R)-1-acetoxy-1-(4-(((2R,4S)-4-carboxy-1-phenylpentan-2-yl)carbamoyl)thiazol-2-yl)-4-methylpentan-3-yl)(methyl)amino)-3-methyl-1-oxopentan-2-yl)carbamoyl)-1-methylpiperidin-1-ium(92). Fmoc-Lys(PEG12)-OSu (59.26 mg, 25 μmol) was added to a flaskcharged with H-ValGluPABQ-Tub (89, 24 mg, 23 μmol) as a solution inanhydrous DMF (0.457 mL) under N₂. N,N-Diisopropylethylamine (16 μL, 91μmol) was added and the reaction was stirred at room temperature for 3hours. The reaction was then quenched with acetic acid (16 μL) andpurified by preparative HPLC to provide 92 (34 mg, 75%). AnalyticalUPLC-MS (system 2): t_(r)=1.35 min, m/z (ES+) calculated 1982.06 (M)⁺,found 1982.37.

(2R)-2-(((2S,3S)-1-(((1R,3R)-1-acetoxy-1-(4-(((2R,4S)-4-carboxy-1-phenylpentan-2-yl)carbamoyl)thiazol-2-yl)-4-methylpentan-3-yl)(methyl)amino)-3-methyl-1-oxopentan-2-yl)carbamoyl)-1-(4-((44S,47S,50S)-44-amino-50-(2-carboxyethyl)-47-isopropyl-38,45,48-trioxo-2,5,8,11,14,17,20,23,26,29,32,35-dodecaoxa-39,46,49-triazahenpentacontanamido)benzyl)-1-methylpiperidin-1-ium(93). To a flask charged with Fmoc-Lys(PEG12)-ValGluPABQ-Tub (92, 34 mg,17 μmol) was added 20% piperidine in DMF (1.7 mL). The reaction wasstirred under N₂ at room temperature for 30 minutes. The reaction wasthen diluted with DMSO/H₂O and purified by preparative HPLC to provide93 (26 mg, 86%). Analytical UPLC-MS (system 2): t_(r)=1.01 min, m/z(ES+) calculated 1759.99 (M)⁺, found 1760.26.

(2R)-2-(((2S,3S)-1-(((1R,3R)-1-acetoxy-1-(4-(((2R,4S)-4-carboxy-1-phenylpentan-2-yl)carbamoyl)thiazol-2-yl)-4-methylpentan-3-yl)(methyl)amino)-3-methyl-1-oxopentan-2-yl)carbamoyl)-1-(4-((44S,47S,50S)-44-((S)-3-((tert-butoxycarbonyl)amino)-2-(2,5-dioxo-2,5-dihydro-1H-pyrrol-1-yl)propanamido)-50-(2-carboxyethyl)-47-isopropyl-38,45,48-trioxo-25,8,11,14,17,20,23,26,29,32,35-dodecaoxa-39,46,49-triazahenpentacontanamido)benzyl)-1-methylpiperidin-1-ium(94). A flask was charged with H-Lys(PEG12)-ValGluPABQ-Tub (93, 26 mg,15 μmol) in anhydrous DMF (0.735 mL), to which mDPR(Boc)-OSu (13, 6 mg,16 μmol) was added as a solid under N₂. N,N-Diisopropylethylamine (10μL, 59 μmol) was added and the reaction was stirred at room temperaturefor 3 hours. The reaction was then quenched with acetic acid (10 μL),diluted with DMSO, and purified by preparative HPLC to provide 94 (16mg, 46%). Analytical UPLC-MS (system 2): t_(r)=1.26 min, m/z (ES+)calculated 2026.08 (M)⁺, found 2026.38.

(2R)-2-(((2S,3S)-1-(((1R,3R)-1-acetoxy-1-(4-(((2R,4S)-4-carboxy-1-phenylpentan-2-yl)carbamoyl)thiazol-2-yl)-4-methylpentan-3-yl)(methyl)amino)-3-methyl-1-oxopentan-2-yl)carbamoyl)-1-(4-((44S,47S,50S)-44-((S)-3-amino-2-(2,5-dioxo-2,5-dihydro-1H-pyrrol-1-yl)propanamido)-50-(2-carboxyethyl)-47-isopropyl-38,45,48-trioxo-2,5,8,11,14,17,20,23,26,29,32,35-dodecaoxa-39,46,49-triazahenpentacontanamido)benzyl)-1-methylpiperidin-1-ium(95). A flask charged with mDPR(Boc)-Lys(PEG12)-ValGluPABQ-Tub (94, 14mg, 7 μmol) was cooled to 0° C. under N₂. A solution of 10% TFA inCH₂Cl₂ (1.03 mL) was added dropwise and stirred for 2 hours. Thereaction was then taken up in DMSO, condensed under reduced pressure,and purified by preparative HPLC to provide 95 (9 mg, 70%). AnalyticalUPLC-MS (system 2): t_(r)=1.03 min, m/z (ES+) calculated 1926.03 (M)⁺,found 1926.32.

(2R)-1-(3-((S)-44-((((9H-fluoren-9-yl)methoxy)carbonyl)amino)-38,45-dioxo-2,5,8,11,14,17,20,23,26,29,32,35-dodecaoxa-39,46-diazanonatetracontanamido)-4-(((2S,3R,4S,5S,6S)-6-carboxy-3,4,5-trihydroxytetrahydro-2H-pyran-2-yl)oxy)benzyl)-2-(((2S,3S)-1-(((1R,3R)-1-acetoxy-1-(4-(((2R,4S)-4-carboxy-1-phenylpentan-2-yl)carbamoyl)thiazol-2-yl)-4-methylpentan-3-yl)(methyl)amino)-3-methyl-1-oxopentan-2-yl)carbamoyl)-1-methylpiperidin-1-ium(96). Fmoc-Lys(PEG12)-OSu (59, 4.4 mg, 4.3 μmol) was added to a flaskcharged with H-GlucQ-Tub (80, 3.9 mg, 3.6 μmol) as a solution inanhydrous DMF (0.355 mL) under N₂. N,N-Diisopropylethylamine (1.9 μL,10.7 μmol) was added and the reaction was stirred at room temperaturefor 3 hours. The reaction was then quenched with acetic acid (1.9 μL)and purified by preparative HPLC to provide 96 (5.0 mg, 70%). AnalyticalUPLC-MS (system 2): t_(r)=1.29 min, m/z (ES+) calculated 2017.02 (M)⁺,found 2017.21.

(2R)-2-(((2S,3S)-1-(((1R,3R)-1-acetoxy-1-(4-(((2R,4S)-4-carboxy-1-phenylpentan-2-yl)carbamoyl)thiazol-2-yl)-4-methylpentan-3-yl)(methyl)amino)-3-methyl-1-oxopentan-2-yl)carbamoyl)-1-(3-((S)-44-amino-38,45-dioxo-2,5,8,11,14,17,20,23,26,29,32,35-dodecaoxa-39,46-diazanonatetracontanamido)-4-(((2S,3R,4S,5S,6S)-6-carboxy-3,4,5-trihydroxytetrahydro-2H-pyran-2-yl)oxy)benzyl)-1-methylpiperidin-1-ium(97). To a flask charged with Fmoc-Lys(PEG12)-GlucQ-Tub (96, 5.0 mg, 2.5μmol) was added 20% piperidine in DMF (0.248 mL). The reaction wasstirred under N₂ at room temperature for 30 minutes. The reaction wasthen diluted with DMSO/H₂O and purified by preparative HPLC to provide97 (3.6 mg, 82%). Analytical UPLC-MS (system 2): t_(r)=0.99 min, m/z(ES+) calculated 1794.95 (M)⁺, found 1795.12.

(2R)-2-(((2S,3S)-1-(((1R,3R)-1-acetoxy-1-(4-(((2R,4S)-4-carboxy-1-phenylpentan-2-yl)carbamoyl)thiazol-2-yl)-4-methylpentan-3-yl)(methyl)amino)-3-methyl-1-oxopentan-2-yl)carbamoyl)-1-(3-((S)-44-((S)-3-((tert-butoxycarbonyl)amino)-2-(2,5-dioxo-2,5-dihydro-1H-pyrrol-1-yl)propanamido)-38,45-dioxo-2,5,8,11,14,17,20,23,26,29,32,35-dodecaoxa-39,46-diazanonatetracontanamido)-4-(((2S,3R,4S,5S,6S)-6-carboxy-3,4,5-trihydroxytetrahydro-2H-pyran-2-yl)oxy)benzyl)-1-methylpiperidin-1-ium(98). A flask was charged with H-Lys(PEG12)-GlucQ-Tub (97, 3.8 mg, 2.14μmol) in anhydrous DMF (0.212 mL), to which mDPR(Boc)-OPFP (44, 1.4 mg,3.2 μmol) was added as a solid under N₂. N,N-Diisopropylethylamine (0.74μL, 4.2 μmol) was added and the reaction was stirred at room temperaturefor 3 hours. The reaction was then quenched with acetic acid (0.74 μL),diluted with DMSO, and purified by preparative HPLC to provide 98 (2.7mg, 61%). Analytical UPLC-MS (system 2): t_(r)=1.20 min, m/z (ES+)calculated 2061.04 (M)⁺, found 2061.20.

(2R)-2-(((2S,3S)-1-(((1R,3R)-1-acetoxy-1-(4-(((2R,4S)-4-carboxy-1-phenylpentan-2-yl)carbamoyl)thiazol-2-yl)-4-methylpentan-3-yl)(methyl)amino)-3-methyl-1-oxopentan-2-yl)carbamoyl)-1-(3-((S)-44-((S)-3-amino-2-(2,5-dioxo-2,5-dihydro-1H-pyrrol-1-yl)propanamido)-38,45-dioxo-2,5,8,11,14,17,20,23,26,29,32,35-dodecaoxa-39,46-diazanonatetracontanamido)-4-(((2S,3R,4S,5S,6S)-6-carboxy-3,4,5-trihydroxytetrahydro-2H-pyran-2-yl)oxy)benzyl)-1-methylpiperidin-1-ium(99). A flask charged with mDPR(Boc)-Lys(PEG12)-GlucQ-Tub (98, 2.7 mg,1.3 μmol) was cooled to 0° C. under N₂. A solution of 10% TFA in CH₂Cl₂(0.26 mL) was added dropwise and stirred for 2 hours. The reaction wasthen taken up in DMSO, condensed under reduced pressure, and purified bypreparative HPLC to provide 99 (2.5 mg, 97%). Analytical UPLC-MS (system2): t_(r)=1.00 min, m/z (ES+) calculated 1960.99 (M)⁺, found 1961.17.

2-((1R,3R)-3-((tert-butoxycarbonyl)(methyl)amino)-1-hydroxy-4-methylpentyl)thiazole-4-carboxylicacid (101). A flask was charged with tubuvaline acetate (Org. Lett.2007, 9, 1605-1607) 100 (225 mg, 560 μmol) dissolved in methanol (5 ml)and tetrahydrofuran (5 ml), then cooled under nitrogen to 0° C. in anice bath. Lithium hydroxide monohydrate (71 mg, 1680 μmol) was dissolvedin water (5 ml) and the solution added dropwise to the reaction flask.The reaction was then stirred at room temperature until UPLC/MS revealedcomplete conversion to product. The material was the diluted withdichloromethane and washed with 0.1 M HCL. The aqueous layer wasextracted twice with dichloromethane, then the combined organics weredried over sodium sulfated, filtered, and concentrated to provide freeacid 101 (200 mg, quant.). Analytical UPLC-MS (system 1): t_(r)=1.33min, m/z (ES+) calculated 359.17 (M+H)⁺, found 359.14.

(2S,4R)-allyl4-(2-((1R,3R)-3-((tert-butoxycarbonyl)(methyl)amino)-1-hydroxy-4-methylpentyl)thiazole-4-carboxamido)-2-methyl-5-phenylpentanoate(102). Tubuvaline free acid 101 (200 mg, 560 μmol) was pre-activated bydissolution in anhydrous dimethylformamide (5.4 ml, 100 mM) and additionof HATU (250 mg, 670 μmol and DIPEA (0.59 ml, 3.36 mmol); the mixturewas then stirred under nitrogen at room temperature for 10 minutes. Theactivated acid was then added to the known (Org. Lett., 2007, 9,1605-1607) tubuphenylalanine allyl ester 16 and the reaction was thenstirred at an ambient temperature under nitrogen, with progressmonitored by UPLC/MS. Upon reaction completion, glacial acetic acid (14equivalents) was then added and the product was purified by preparativeHPLC to provide Tuv(OH)-Tup-O-allyl dipeptide 102 (272 mg, 83%).Analytical UPLC-MS (system 1): t_(r)=1.84 min, m/z (ES+) calculated588.31 (M+H)⁺, found 588.29.

(2S,4R)-allyl4-(2-((1R,3R)-3-((tert-butoxycarbonyl)(methyl)amino)-4-methyl-1-(propionyloxy)pentyl)thiazole-4-carboxamido)-2-methyl-5-phenylpentanoate(105). Tuv(OH)-Tup-O-allyl dipeptide 102 (26 mg, 44 μmol) was dissolvedin anhydrous pyridine (1.8 ml, 25 mM) and stirred under a nitrogenatmosphere at room temperature. Propionic anhydride 103 (113 μl, 20equivalents) was added dropwise and the reaction was then monitored byUPLC/MS. Additional propionic anhydride (20 equivalents) was added toachieve conversion to product. The material was the diluted withdichloromethane and washed with 0.1 M HCl. The aqueous layer wasextracted twice with dichloromethane, then the combined organics weredried over sodium sulfated, filtered, and concentrated to provide thecrude product, which was subsequently purified by preparative HPLC toprovide the esterified product 105 (17 mg, 61%). Analytical UPLC-MS(system 1): t_(r)=1.99 min, m/z (ES+) calculated 644.34 (M+H)⁺, found644.26.

(2S,4R)-allyl4-(2-((1R,3R)-3-((tert-butoxycarbonyl)(methyl)amino)-1-(butyryloxy)-4-methylpentyl)thiazole-4-carboxamido)-2-methyl-5-phenylpentanoate(106). Tuv(OH)-Tup-O-allyl dipeptide 102 (27 mg, 46 μmol) was dissolvedin anhydrous pyridine (0.9 ml, 50 mM) and stirred under a nitrogenatmosphere at room temperature. Butyric anhydride 104 (225 μl, 30equivalents) was added dropwise and the reaction was then monitored byUPLC/MS. Additional butyric anhydride (40 equivalents) was added inthree portions to achieve conversion to product. The material was thediluted with dichloromethane and washed with 0.1 M HCl. The aqueouslayer was extracted twice with dichloromethane, then the combinedorganics were dried over sodium sulfated, filtered, and concentrated toprovide the crude product, which was subsequently purified bypreparative HPLC to provide the esterified product 106 (24 mg, 80%).Analytical UPLC-MS (system 1): t_(r)=2.13 min, m/z (ES+) calculated658.35 (M+H)⁺, found 658.23.

(2S,4R)-allyl4-(2-((1R,3R)-3-((tert-butoxycarbonyl)(methyl)amino)-1-(isobutyryloxy)-4-methylpentyl)thiazole-4-carboxamido)-2-methyl-5-phenylpentanoate(108). Tuv(OH)-Tup-O-allyl dipeptide 102 (26 mg, 44 μmol) was dissolvedin anhydrous pyridine (1.8 ml, 25 mM) and stirred under a nitrogenatmosphere at room temperature. Isobutyryl chloride 107 (93 μl, 20equivalents) was added dropwise and the reaction was then monitored byUPLC/MS. Upon conversion to product, the material was then diluted withdichloromethane and washed with 0.1 M HCl. The aqueous layer wasextracted twice with dichloromethane, then the combined organics weredried over sodium sulfated, filtered, and concentrated to provide thecrude product, which was subsequently purified by preparative HPLC toprovide the esterified product 108 (29 mg, quant.). Analytical UPLC-MS(system 1): t_(r)=2.13 min, m/z (ES+) calculated 658.35 (M+H)⁺, found658.33.

(2S,4R)-allyl4-(2-((1R,3R)-3-((tert-butoxycarbonyl)(methyl)amino)-4-methyl-1-((3-methylbutanoyl)oxy)pentyl)thiazole-4-carboxamido)-2-methyl-5-phenylpentanoate(111). A flask was charged with isovaleric acid 109 (94 μl, 851 μmol)dissolved in anhydrous dichloromethane (5.6 ml, 15 mM) and the solutionwas stirred at 0 C under a nitrogen atmosphere. DMAP (10 mg, 85 μmol)was then added, followed by DCC (88 mg, 425 μmol), and the reaction wasallowed to warm to room temperature over 2 hours. The resultingactivated acid was then added to Tuv(OH)-Tup-O-allyl dipeptide 102 (50mg, 85 μmol) and the reaction was stirred overnight, at which timeUPLC/MS revealed conversion to product. The reaction was then dilutedwith dichloromethane and washed with 0.1 M HCl. The aqueous layer wasextracted twice with dichloromethane, then the combined organics weredried over sodium sulfated, filtered, and concentrated to provide thecrude product, which was subsequently purified by preparative HPLC toprovide the esterified product 111 (52 mg, 91%). Analytical UPLC-MS(system 2): t_(r)=1.91 min, m/z (ES+) calculated 672.37 (M+H)⁺, found672.46.

(2S,4R)-allyl4-(2-((1R,3R)-3-((tert-butoxycarbonyl)(methyl)amino)-1-((3,3-dimethylbutanoyl)oxy)-4-methylpentyl)thiazole-4-carboxamido)-2-methyl-5-phenylpentanoate(112). A flask was charged with gem-dimethylbutyric acid 110 (98 μl, 766μmol) dissolved in anhydrous dichloromethane (5.1 ml, 15 mM) and thesolution was stirred at 0 C under a nitrogen atmosphere. DMAP (9 mg, 77μmol) was then added, followed by DCC (79 mg, 383 μmol), and thereaction was allowed to warm to room temperature over 2 hours. Theresulting activated acid was then added to Tuv(OH)-Tup-O-allyl dipeptide102 (45 mg, 77 μmol) and the reaction was stirred overnight, at whichtime UPLC/MS revealed conversion to product. The reaction was thendiluted with dichloromethane and washed with 0.1 M HCl. The aqueouslayer was extracted twice with dichloromethane, then the combinedorganics were dried over sodium sulfated, filtered, and concentrated toprovide the crude product, which was subsequently purified bypreparative HPLC to provide the esterified product 112 (49 mg, 93%).Analytical UPLC-MS (system 2): t_(r)=1.88 min, m/z (ES+) calculated686.39 (M+H)⁺, found 686.47.

General procedure for the Hoc deprotection of Tuv(O-ester)-TupIntermediates. Esterified tubuvaline-tubuphenylalanine intermediates105, 106, 108, 111, or 112 were deprotected to reveal the secondaryamine functional group under acidic conditions with 10% TFA indichloromethane (25 mM). Specifically, the starting material wasdissolve in anhydrous dichloromethane (9 volumes) and stirred undernitrogen at 0 C. Trifluoroacetic acid (I volume) was then added dropwiseto the Stirred solution. The reaction was warmed slowly to roomtemperature and monitored by UPLC/MS. Upon completion, the reaction wasconcentrated by rotary evaporation and pumped down on a vacuum lineovernight. The free amines 135-139 were carried forward without furtherpurification.

(2S,4R)-allyl2-methyl-4-(2-((1R,3R)-4-methyl-3-(methylamino)-1-(propionyloxy)pentyl)thiazole-4-carboxamido)-5-phenylpentanoate(113): Boc-protected Tuv-Tup intermediate 105 (17 mg, 26 μmol) wasdeprotected as described above to provide 14 mg (quant.) of the titlecompound. UPLC-MS (system 1): t_(r)=1.24 min, m/z (ES+) calculated544.29 (M+H)⁺, found 544.25.

(2S,4R)-allyl4-(2-((1R,3R)-1-(butyryloxy)-4-methyl-3-(methylamino)pentyl)thiazole-4-carboxamido)-2-methyl-5-phenylpentanoate(114): Boc-protected Tuv-Tup intermediate 106 (24 mg, 37 μmol) wasdeprotected as described above to provide 21 mg (quant.) of the titlecompound. UPLC-MS (system 2): t_(r)=1.20 min, m/z (ES+) calculated558.30 (M+H)⁺, found 558.38.

(2S,4R)-allyl4-(2-((1R,3R)-1-(isobutyryloxy)-4-methyl-3-(methylamino)pentyl)thiazole-4-carboxamido)-2-methyl-5-phenylpentanoate(115): Boc-protected Tuv-Tup intermediate 108 (29 mg, 44 μmol) wasdeprotected as described above to provide 25 mg (quant.) of the titlecompound. UPLC-MS (system 1): t_(r)=1.30 min, m/z (ES+) calculated558.30 (M+H)⁺, found 557.93.

(2S,4R)-allyl2-methyl-4-(2-((1R,3R)-4-methyl-3-(methylamino)-1-((3-methylbutanoyl)oxy)pentyl)thiazole-4-carboxamido)-5-phenylpentanoate(116): Boc-protected Tuv-Tup intermediate 111 (52 mg, 78 μmol) wasdeprotected as described above to provide 45 mg (quant.) of the titlecompound. UPLC-MS (system 2): t_(r)=1.23 min, m/z (ES+) calculated572.32 (M+H)⁺, found 572.40.

(2S,4R)-allyl4-(2-((1R,3R)-1-((3,3-dimethylbutanoyl)oxy)-4-methyl-3-(methylamino)pentyl)thiazole-4-carboxamido)-2-methyl-5-phenylpentanoate(117): Boc-protected Tuv-Tup intermediate 112 (49 mg, 71 μmol) wasdeprotected as described above to provide 46 mg (quant.) of the titlecompound. UPLC-MS (system 2): t_(r)=1.27 min. m/z (ES+) calculated586.33 (M+H)⁺, found 586.42.

General procedure for the amide coupling of O-esterifiedtubuvaline-tubuphenylalanine dipeptides with Fmoc-protectedL-isoleucine. Commercially available Fmoc-L-Isoleucine (4 equivalents)was dissolved in anhydrous dimethylformamide (50 mM) and pre-activatedwith HATU (4 equivalents) and DIPEA (8 equivalents); the mixture wasstirred for 10 minutes at room temperature under nitrogen. The activatedacid was then added to the Tuv(O-ester)-Tup dipeptides 113-117; thereaction was stirred at room temperature under nitrogen and monitored byUPLC/MS. Once the reaction had stopped progressing or had reachedcompletion, glacial acetic acid (13 equivalents) was added and thereaction was purified by prep HPLC.

(2S,4R)-allyl4-(2-((5S,8R,10R)-5-((S)-sec-butyl)-1-(9H-fluoren-9-yl)-8-isopropyl-7-methyl-3,6,12-trioxo-2,11-dioxa-4,7-diazatetradecan-10-yl)thiazole-4-carboxamido)-2-methyl-5-phenylpentanoate(118): Tuv-Tup intermediate 113 (14 mg, 25 μmol) was coupled toFmoc-L-Ile as described above to provide 17 mg (77%) of the titlecompound. UPLC-MS (system 1): t_(r)=2.11 min, m/z (ES+) calculated879.44 (M+H)⁺, found 879.60.

(2S,4R)-allyl4-(2-((5S,8R,10R)-5-((S)-sec-butyl)-1-(9H-fluoren-9-yl)-8-isopropyl-7-methyl-3,6,12-trioxo-2,11-dioxa-4,7-diazapentadecan-10-yl)thiazole-4-carboxamido)-2-methyl-5-phenylpentanoate(119): Tuv-Tup intermediate 114 (21 mg, 37 μmol) was coupled toFmoc-L-Ile as described above to provide 24 mg (73%) of the titlecompound. UPLC-MS (system 2): t_(r)=1.94 min, m/z (ES+) calculated893.45 (M+H)⁺, found 893.56.

(2S,4R)-allyl4-(2-((5S,8R,10R)-5-((S)-sec-butyl)-1-(9H-fluoren-9-yl)-8-isopropyl-7,13-dimethyl-3,6,12-trioxo-2,11-dioxa-4,7-diazatetradecan-10-yl)thiazole-4-carboxamido)-2-methyl-5-phenylpentanoate(120): Tuv-Tup intermediate 115 (25 mg, 44 μmol) was coupled toFmoc-L-Ile as described above to provide 26 mg (67%) of the titlecompound. UPLC-MS (system 2): t_(r)=1.85 min, m/z (ES+) calculated893.45 (M+H)⁺, found 893.56.

(2S,4R)-allyl4-(2-((5S,8R,10R)-5-((S)-sec-butyl)-1-(9H-fluoren-9-yl)-8-isopropyl-7,14-dimethyl-3,6,12-trioxo-2,11-dioxa-4,7-diazapentadecan-10-yl)thiazole-4-carboxamido)-2-methyl-5-phenylpentanoate(121): Tuv-Tup intermediate 116 (45 mg, 79 μmol) was coupled toFmoc-L-Ile as described above to provide 54 mg (75%) of the titlecompound. UPLC-MS (system 2): t_(r)=2.06 min, m/z (ES+) calculated907.47 (M+H)⁺, found 907.58.

(2S,4R)-allyl4-(2-((5S,8R,10R)-5-((S)-sec-butyl)-1-(9H-fluoren-9-yl)-8-isopropyl-7,14,14-trimethyl-3,6,12-trioxo-2,11-dioxa-4,7-diazapentadecan-10-yl)thiazole-4-carboxamido)-2-methyl-5-phenylpentanoate(122): Tuv-Tup intermediate 117 (46 mg, 79 μmol) was coupled toFmoc-L-Ile as described above to provide 55 mg (75%) of the titlecompound. UPLC-MS (system 2): t_(r)=2.50 min, m/z (ES+) calculated921.49 (M+H)⁺, found 921.59.

General procedure for the Fmoc-deprotection of isoleucine-O-esterifiedtubuvaline-tubuphenylalanine tripeptides. Fmoc-Ile-Tuv(O-ester)-Tupallyl ester (118-122) was treated with 20% piperidine indimethylformamide (20 mM), with stirring under nitrogen at roomtemperature. Once complete deprotection had been achieved, as monitoredby UPLC/MS, the reaction mixture was concentrated by rotary evaporation.The crude product was then purified by preparative HPLC to provide freeamine tripeptides 145-149.

(2S,4R)-allyl4-(2-((1R,3R)-3-((2S,3S)-2-amino-N,3-dimethylpentanamido)-4-methyl-1-(propionyloxy)pentyl)thiazole-4-carboxamido)-2-methyl-5-phenylpentanoate(123): Fmoc-Ile-Tuv-Tup intermediate 118 (17 mg, 19 μmol) wasdeprotected as described above to provide 15 mg (quant.) of the titlecompound. UPLC-MS (system 1): t_(r)=1.29 min, m/z (ES+) calculated657.37 (M+H)⁺, found 658.04.

(2S,4R)-allyl4-(2-((1R,3R)-3-((2S,3S)-2-amino-N,3-dimethylpentanamido)-1-(butyryloxy)-4-methylpentyl)thiazole-4-carboxamido)-2-methyl-5-phenylpentanoate(124): Fmoc-Ile-Tuv-Tup intermediate 119 (23 mg, 26 μmol) wasdeprotected as described above to provide 15 mg (86%) of the titlecompound. UPLC-MS (system 2): t_(r)=1.24 min, n/(ES+) calculated 671.39(M+H)⁺, found 671.48.

(2S,4R)-allyl4-(2-((1R,3R)-3-((2S,3S)-2-amino-N,3-dimethylpentanamido)-1-(isobutyryloxy)-4-methylpentyl)thiazole-4-carboxamido)-2-methyl-5-phenylpentanoate(125): Fmoc-Ile-Tuv-Tup intermediate 120 (26 mg, 29 μmol) wasdeprotected as described above to provide 20 mg (quant.) of the titlecompound. UPLC-MS (system 1): t_(r)=1.33 min, m/z (ES+) calculated671.39 (M+H)⁺, found 671.33.

(2S,4R)-allyl4-(2-((1R,3R)-3-((2S,3S)-2-amino-N,3-dimethylpentanamido)-4-methyl-1-((3-methylbutanoyl)oxy)pentyl)thiazole-4-carboxamido)-2-methyl-5-phenylpentanoate(126): Fmoc-Ile-Tuv-Tup intermediate 121 (54 mg, 60 μmol) wasdeprotected as described above to provide 41 mg (quant.) of the titlecompound. UPLC-MS (system 2): t_(r)=1.31 min. m/z (ES+) calculated685.40 (M+H)⁺, found 685.49.

(2S,4R)-allyl4-(2-((1R,3R)-3-((2S,3S)-2-amino-N,3-dimethylpentanamido)-1-((3,3-dimethylbutanoyl)oxy)-4-methylpentyl)thiazole-4-carboxamido)-2-methyl-5-phenylpentanoate(127): Fmoc-le-Tuv-Tup intermediate 122 (55 mg, 60 μmol) was deprotectedas described above to provide 36 mg (86%) of the title compound. UPLC-MS(system 2): t_(r)=1.30 min, m/z (ES+) calculated 699.42 (M+H)⁺, found699.51.

General procedure for the amide coupling ofisoleucine-tubuvaline(O-ester)-tubuphenylalanine tripeptides with(R)—N-methyl-pipecolic acid. Commercially available(R)—N-methyl-pipecolic acid (D-Mep) 36 (2 equivalents) was dissolved inanhydrous dimethylformamide (20-25 mM) and pre-activated with HATU (2equivalents) and DIPEA (4 equivalents); the mixture was stirred for 10minutes at room temperature under nitrogen. The activated acid was thenadded to the Ile-Tuv(O-ester)-Tup tripeptides 123-127; the reaction wasstirred at room temperature under nitrogen and monitored by UPLC/MS.Upon reaction completion, glacial acetic acid (14 equivalents) was thenadded and the product was purified by preparative HPLC.

(2S,4R)-allyl4-(2-((1R,3R)-3-((2S,3S)—N,3-dimethyl-2-((R)-1-methylpiperidine-2-carboxamido)pentanamido)-4-methyl-1-(propionyloxy)pentyl)thiazole-4-carboxamido)-2-methyl-5-phenylpentanoate(128): Ile-Tuv-Tup intermediate 123 (5 mg, 8 μmol) was coupled to D-Mep36 as described above to provide 6 mg (97%) of the title compound.UPLC-MS (system 1): t_(r)=1.33 min, m/z (ES+) calculated 782.45 (M+H)⁺,found 781.82.

(2S,4R)-allyl4-(2-((1R,3R)-1-(butyryloxy)-3-((2S,3S)—N,3-dimethyl-2-((R)-1-methylpiperidine-2-carboxamido)pentanamido)-4-methylpentyl)thiazole-4-carboxamido)-2-methyl-5-phenylpentanoate(129): Ile-Tuv-Tup intermediate 124 (6 mg, 9 μmol) was coupled to D-Mep36 as described above to provide 7 mg (98%) of the title compound.UPLC-MS (system 2): t_(r)=1.31 min, m/z (ES+) calculated 796.47 (M+H)⁺,found 796.57.

(2S,4R)-allyl4-(2-((1R,3R)-3-((2S,3S)—N,3-dimethyl-2-((R)-1-methylpiperidine-2-carboxamido)pentanamido)-1-(isobutyryloxy)-4-methylpentyl)thiazole-4-carboxamido)-2-methyl-5-phenylpentanoate(130): Ile-Tuv-Tup intermediate 125 (5 mg, 8 μmol was coupled to D-Mep36 as described above to provide 6 mg (94%) of the title compound.UPLC-MS (system 1): t_(r)=1.37 min, m/z (ES+) calculated 796.47 (M+H)⁺,found 795.78.

(2S,4R)-allyl4-(2-((1R,3R)-3-((2S,3S)—N,3-dimethyl-2-((R)-1-methylpiperidine-2-carboxamido)pentanamido)-4-methyl-1-((3-methylbutanoyl)oxy)pentyl)thiazole-4-carboxamido)-2-methyl-5-phenylpentanoate(131): Ile-Tuv-Tup intermediate 126 (7 mg, 10 μmol) was coupled to D-Mep36 as described above to provide 6 mg (94%) of the title compound.UPLC-MS (system 2): t_(r)=1.35 min, m/z (ES+) calculated 810.49 (M+H)⁺,found 810.59.

(2S,4R)-allyl4-(2-((1R,3R)-3-((2S,3S)—N,3-dimethyl-2-((R)-1-methylpiperidine-2-carboxamido)pentanamido)-1-((3,3-dimethylbutanoyl)oxy)-4-methylpentyl)thiazole-4-carboxamido)-2-methyl-5-phenylpentanoate(132): Ile-Tuv-Tup intermediate 127 (7 mg, 10 μmol) was coupled to D-Mep36 as described above to provide 6 mg (94%) of the title compound.UPLC-MS (system 2): t_(r)=1.38 min, m/z (ES+) calculated 824.50 (M+H)⁺,found 824.60.

General procedure for the allyl ester removal from D-methylpipecolicacid-isoleucine-tubuvaline(O-ester)-tubuphenylalanine intermediates.Allyl ester-protected tubulysin intermediate (128-132) was dissolved inanhydrous dichloromethane (20 mM) treated with palladiumtetrakis(triphenylphosphine) (0.1 equiv.), triphenylphosphine (0.2equivalents), and anhydrous pyrrolidine (8 equivalents), and thereaction was stirred at an ambient temperature under nitrogen. OnceUPLC/MS revealed conversion to the product free acid, the reaction wasquenched with glacial acetic acid (22 equivalents), diluted withacetonitrile and dimethylformamide, and then concentrated by rotaryevaporation. The crude tubulysin ether was then purified by preparativeHPLC.

(2S,4R)-4-(2-((1R,3R)-3-((2S,3S)—N,3-dimethyl-2-((R)-1-methylpiperidine-2-carboxamido)pentanamido)-4-methyl-1-(propionyloxy)pentyl)thiazole-4-carboxamido)-2-methyl-5-phenylpentanoicacid (133): Allyl ester-protected tubulysin intermediate 128 (6 mg, 8μmol) was deprotected as described above to provide 3.8 mg (67%) oftubulysin 133 (Tub propionate). UPLC-MS (system 2): t_(r)=1.11 min, m/z(ES+) calculated 742.42 (M+H)⁺, found 742.51.

(2S,4R)-4-(2-((1R,3R)-1-(butyryloxy)-3-((2S,3S)—N,3-dimethyl-2-((R)-1-methylpiperidine-2-carboxamido)pentanamido)-4-methylpentyl)thiazole-4-carboxamido)-2-methyl-5-phenylpentanoicacid (134): Allyl ester-protected tubulysin intermediate 129 (7 mg, 9μmol) was deprotected as described above to provide 6 mg (88%) oftubulysin 134 (Tub butyrate). UPLC-MS (system 2): t_(r)=1.16 min, m/z(ES+) calculated 756.44 (M+H)⁺, found 756.54.

(2S,4R)-4-(2-((1R,3R)-3-((2S,3S)—N,3-dimethyl-2-((R)-1-methylpiperidine-2-carboxamido)pentanamido)-1-(isobutyryloxy)-4-methylpentyl)thiazole-4-carboxamido)-2-methyl-5-phenylpentanoicacid (135): Allyl ester-protected tubulysin intermediate 130 (6 mg, 8μmol) was deprotected as described above to provide 3 mg (50%) oftubulysin 135 (Tub isobutyrate). UPLC-MS (system 1): t_(r)=1.23 min. m/z(ES+) calculated 756.44 (M+H)⁺, found 756.82.

(2S,4R)-4-(2-((1R,3R)-3-((2S,3S)—N,3-dimethyl-2-((R)-1-methylpiperidine-2-carboxamido)pentanamido)-4-methyl-1-((3-methylbutanoyl)oxy)pentyl)thiazole-4-carboxamido)-2-methyl-5-phenylpentanoicacid (136): Allyl ester-protected tubulysin intermediate 131 (7 mg, 9μmol) was deprotected as described above to provide 7 mg (quant.) oftubulysin 136 (Tub isovalerate). UPLC-MS (system 2): t_(r)=1.22 min, m/z(ES+) calculated 770.45 (M+H)⁺. found 770.55.

(2S,4R)-4-(2-((1R,3R)-3-((2S,3S)—N,3-dimethyl-2-((R)-1-methylpiperidine-2-carboxamido)pentanamido)-1-((3,3-dimethylbutanoyl)oxy)-4-methylpentyl)thiazole-4-carboxamido)-2-methyl-5-phenylpentanoicacid (137): Allyl ester-protected tubulysin intermediate 132 (7 mg, 8.5μmol) was deprotected as described above to provide 8 mg (quant.) oftubulysin 137 (Tub gem-dimethylbutyrate). UPLC-MS (system 2): t_(r)=1.23min, m/z (ES+) calculated 784.47 (M+H)⁺, found 784.57.

(2R)-1-(3-(3-((((9H-fluoren-9-yl)methoxy)carbonyl)amino)propanamido)-4-(((2S,3R,4S,5S,6S)-6-((allyloxy)carbonyl)-3,4,5-trihydroxytetrahydro-2H-pyran-2-yl)oxy)benzyl)-2-(((2S,3S)-1-(((1R,3R)-1-(4-(((2R,4S)-5-(allyloxy)-4-methyl-5-oxo-1-phenylpentan-2-yl)carbamoyl)thiazol-2-yl)-1-(Isobutyryloxy)-4-methylpentan-3-yl)(methyl)amino)-3-methyl-1-oxopentan-2-yl)carbamoyl)-1-methylpiperidin-1-ium(138). To a flask charged with H-Ile-Tuv(O-isobutyrate)-Tup-OAllyl (125,15 mg, 22 μmol) was added Fmoc-Gluc(Allyl)Q-Mep-OH (78, 17 mg, 22 μmol)and HATU (9 mg, 22 μmol) as solids followed by DMF (0.9 ml).N,N-Diisopropylethylamine (15 μl, 88 μmol) was added and the reactionwas stirred at room temperature and monitored by UPLC/MS. The reactionwas then taken up in DMSO and purified by preparative HPLC to provide138 (4 mg, 13%). Analytical UPLC-MS (system 1): t_(r)=1.53 min, m/z(ES+) calculated 1426.69 (M)⁺, found 1426.17.

(2R)-1-(3-(3-aminopropanamido)-4-(((2S,3R,4S,5S,6S)-6-carboxy-3,4,5-trihydroxytetrahydro-2H-pyran-2-yl)oxy)benzyl)-2-(((2S,3S)-1-(((1R,3R)-1-(4-(((2R,4S)-4-carboxy-1-phenylpentan-2-yl)carbamoyl)thiazol-2-yl)-1-(isobutyryloxy)-4-methylpentan-3-yl)(methyl)amino)-3-methyl-1-oxopentan-2-yl)carbamoyl)-1-methylpiperidin-1-ium(139). Fmoc-Gluc(Allyl)Q-Tub(iso-O-Allyl) (138.4 mg, 3 μmol) was takenup in DCM (0.3 ml) stirring under N₂. Pd(PPh₃)₄ (0.4 mg, 0.3 μmol) andPPh₃ (0.2 mg, 0.6 μmol) were added as solids followed by pyrrolidine (2μl, 24 μmol). The reaction was stirred to 2 hours at room temperature,then taken up in DMSO, condensed under reduced pressure, and purified bypreparative HPLC to provide 139 (3 mg, 88%). Analytical UPLC-MS (system1): t_(r)=1.04 min, m/z (ES+) calculated 1124.56 (M)⁺, found 1124.69.

(2R)-1-(3-((S)-44-((((9H-fluoren-9-yl)methoxy)carbonyl)amino)-38,45-dioxo-2,5,8,11,14,17,20,23,26,29,32,35-dodecaoxa-39,46-diazanonatetracontanamido)-4-(((2S,3R,4S,5S,6S)-6-carboxy-3,4,5-trihydroxytetrahydro-2H-pyran-2-yl)oxy)benzyl)-2-(((2S,3S)-1-(((1R,3R)-1-(4-(((2R,4S)-4-carboxy-1-phenylpentan-2-yl)carbamoyl)thiazol-2-yl)-1-(isobutyryloxy)-4-methylpentan-3-yl)(methyl)amino)-3-methyl-1-oxopentan-2-yl)carbamoyl)-1-methylpiperidin-1-ium(140). Fmoc-Lys(PEG12)-OSu (59, 10 mg, 9 μmol) was added to a flaskcharged with H-GlucQ-Tub(iso-O-allyl) (139, 3 mg, 3 μmol) as a solutionin anhydrous DMF (0.3 ml) under N₂. N,N-Diisopropylethylamine (2 μl, 9μmol) was added and the reaction was stirred at room temperature for 3hours. The reaction was then quenched with acetic acid and purified bypreparative HPLC to provide 140 (0.8 mg, 13%). Analytical UPLC-MS(system 2): t_(r)=1.35 min, m/z (ES+) calculated 1023.03 (M+H)²⁺, found1023.15.

(2R)-1-(3-((S)-44-amino-38,45-dioxo-2,5,8,11,14,17,20,23,26,29,32,35-dodecaoxa-39,46-diazanonatetracontanamido)-4-(((2S,3R,4S,5S,6S)-6-carboxy-3,4,5-trihydroxytetrahydro-2H-pyran-2-yl)oxy)benzyl)-2-(((2S,3S)-1-(((1R,3R)-1-(4-(((2R,4S)-4-carboxy-1-phenylpentan-2-yl)carbamoyl)thiazol-2-yl)-1-(isobutyryloxy)-4-methylpentan-3-yl)(methyl)amino)-3-methyl-1-oxopentan-2-yl)carbamoyl)-1-methylpiperidin-1-ium(141). To a flask charged with Fmoc-Lys(PEG12)-GlucQ-Tub-(O-iso-allyl)(140, 0.8 mg, 0.4 μmol) was added 20% piperidine in DMF (0.2 ml). Thereaction was stirred under N₂ at room temperature for 2 hours. Thereaction was then diluted with DMSO/H₂O and purified by preparative HPLCto provide 141 (3.6 mg, 82%). Analytical UPLC-MS (system 2): t_(r)=1.07min, m/z (ES+) calculated 1822.98 (M)⁺, found 1823.15.

(2R)-1-(3-((S)-44-((S)-3-((tert-butoxycarbonyl)amino)-2-(2,5-dioxo-2,5-dihydro-1H-pyrrol-1-yl)propanamido)-38,45-dioxo-2,5,8,11,14,17,20,23,26,29,32,35-dodecaoxa-39,46-diazanonatetracontanamido)-4-(((2S,3R,4S,5S,6S)-6-carboxy-3,4,5-trihydroxytetrahydro-2H-pyran-2-yl)oxy)benzyl)-2-(((2S,3S)-1-(((1R,3R)-1-(4-(((2R,4S)-4-carboxy-1-phenylpentan-2-yl)carbamoyl)thiazol-2-yl)-1-(isobutyryloxy)-4-methylpentan-3-yl)(methyl)amino)-3-methyl-1-oxopentan-2-yl)carbamoyl)-1-methylpiperidin-1-ium(142). A flask was charged with H-Lys(PEG12)-GlucQ-Tub-(O-iso-allyl)(141, 0.5 mg, 0.4 μmol) in anhydrous DMF (0.212 nil), to whichmDPR(Boc)-OPFP (44, 1.4 mg, 3.2 μmol) was added as a solid under N₂.N,N-Diisopropylethylamine (0.74 μl, 4.2 μmol) was added and the reactionwas stirred at room temperature for 3 hours. The reaction was thenquenched with acetic acid, diluted with DMSO, and purified bypreparative HPLC to provide 142 (0.5 mg, 61%). Analytical UPLC-MS(system 2): t_(r)=1.25 min, m/z (ES+) calculated 1045.04 (M+H)⁺. found1045.16.

(2R)-1-(3-((S)-44-((S)-3-amino-2-(2,5-dioxo-2,5-dihydro-1H-pyrrol-1-yl)propanamido)-38,45-dioxo-2,5,8,11,14,17,20,23,26,29,32,35-dodecaoxa-39,46-diazanonatetracontanamido)-4-(((2S,3R,4S,5S,6S)-6-carboxy-3,4,5-trihydroxytetrahydro-2H-pyran-2-yl)oxy)benzyl)-2-(((2S,3S)-1-(((1R,3R)-1-(4-(((2R,4S)-4-carboxy-1-phenylpentan-2-yl)carbamoyl)thiazol-2-yl)-1-(isobutyryloxy)-4-methylpentan-3-yl)(methyl)amino)-3-methyl-1-oxopentan-2-yl)carbamoyl)-1-methylpiperidin-1-ium(143). A flask charged with mDPR(Boc)-Lys(PEG12)-GlucQ-Tub(O-iso-allyl)(142, 0.5 mg, 0.24 μmol) was cooled to 0° C. under N₂. A solution of 10%TFA in CH₂Cl₂ (0.26 ml) was added dropwise and stirred for 2 hours. Thereaction was then taken up in DMSO, condensed under reduced pressure,and purified by preparative HPLC to provide 143 (0.7 mg, quant.).Analytical UPLC-MS (system 2): t_(r)=1.06 min, m/z (ES+) calculated1989.02 (M)⁺, found 1989.20.

General procedure for the etherification of tubuvaline. A flame-driedflask was charged with the Boc-protected known tubuvaline (J. Org.Chem., 2008, 73, 4362-4369) intermediate 17 (or 186) in anhydroustetrahydrofuran (50 mM), to which was added 18-crown-6 (2.0 equivalents)and cooled to −78 C. Potassium hexamethyldisilazide (1.5 equivalents) asa 1 M solution in tetrahydrofuran was added dropwise and the reactionwas then stirred for 1 hour at -78 C under nitrogen. Unsaturatedbromoalkane (2 equivalents) was then added and the reaction slowlywarmed to room temperature and followed by UPLC/MS. Once the startingmaterial was consumed, the reaction was cooled on ice and quenched withsaturated ammonium chloride and diluted in dichloromethane (10 volumes).The organic layer was washed with 0.1 M HCl and the resulting aqueousphase extracted twice with dichloromethane. The combined organics werethen dried over sodium sulfate, filtered, and concentrated to dryness.Purification of the crude O-alkylated products was achieved by flashchromatography over silica gel or preparative HPLC.

Ethyl2-((1R,3R)-3-((tert-butoxycarbonyl)(methyl)amino)-4-methyl-1-((2-methylallyl)oxy)pentyl)thiazole-4-carboxylate(148): Propyl ester protected tubuvaline intermediate 186 (299 mg, 750μmol) was O-alkylated as described above with 3-bromo-2-methylprop-1-ene(151 μl, 1.5 mmol) to provide 243 mg (71%) of the title compound aftersilica gel purification eluting methanol and dichloromethane mixtures.UPLC-MS (system 2): t_(r)=1.77 min, m/z (ES+) calculated 455.26 (M+H)⁺,found 455.32.

Ethyl2-((1R,3R)-1-(allyloxy)-3-((tert-butoxycarbonyl)(methyl)amino)-4-methylpentyl)thiazole-4-carboxylate(149): Tubuvaline intermediate 17 (84 mg, 218 μmol) was O-allylated asdescribed above with allyl bromide (40 μl, 436 μmol) to provide 77 mg(83%) of the title compound after silica gel purification elutingmethanol and dichloromethane mixtures. UPLC-MS (system 2): t_(r)=1.69min, m/z (ES+) calculated 427.23 (M+H)⁺, found 427.30.

Ethyl2-((1R,3R)-3-((tert-butoxycarbonyl)(methyl)amino)-4-methyl-1-(prop-2-yn-1-yloxy)pentyl)thiazole-4-carboxylate(150): Tubuvaline intermediate 17 (101 mg, 262 μmol) was O-propargylatedas described above with propargyl bromide (56 μl, 524 μmol) to provide76 mg (68%) of the title compound after purification. UPLC-MS (system2): t_(r)=1.63 min, m/z (ES+) calculated 425.21 (M+H)⁺, found 425.28.

Ethyl2-((1R,3R)-1-(benzyloxy)-3-((tert-butoxycarbonyl)(methyl)amino)-4-methylpentyl)thiazole-4-carboxylate(151): Tubuvaline intermediate 17 (90 mg, 230 μmol) was O-benzylated asdescribed above with benzyl bromide (55 μl, 460 μmol) to provide 21 mg(19%) of the tide compound after purification. UPLC-MS (system 1):t_(r)=1.95 min, m/z. (ES+) calculated 477.24 (M+H)⁺, found 477.22.

General procedure for the saponification of O-alkylated tubuvalineesters. Saponification reactions were carried out at 20 mM reactionconcentration using a 1:1:1 mixture of tetrahydrofuran:methanol:watersolvent mixture. O-alkylated tubuvaline intermediates 148-151 weredissolved in 1 volume each tetrahydrofuran and methanol. The mixture wasthen cooled in an ice bath at 0 C. Lithium hydroxide monohydrate (2-3equivalents) was dissolved in 1 volume of distilled water and addeddropwise to the reaction flask, with stirring at 0 C. The reaction wasthen allowed to warm up to room temperature and monitored by UPLC/MS.Once the starting material had converted to free acid, the reaction wasquenched with glacial acetic acid (2-3 equivalents) and concentrated byrotary evaporation. The crude carboxylic acids were then purified bypreparative HPLC.

2-((1R,3R)-3-((tert-butoxycarbonyl)(methyl)amino)-4-methyl-1-((2-methylallyl)oxy)pentyl)thiazole-4-carboxylicacid (152): Tubuvaline ether intermediate 148 (143 mg, 315 μmol) wassaponified as described above with lithium hydroxide monohydrate (27 mg,630 μmol) to provide 114 mg (88%) of the title compound. UPLC-MS (system1): t_(r)=1.57 min, m/z (ES+) calculated 413.21, found 413.28.

2-((1R,3R)-1-(allyloxy)-3-((tert-butoxycarbonyl)(methyl)amino)-4-methylpentyl)thiazole-4-carboxylicacid (153): Tubuvaline allyl ether intermediate 149 (77 mg, 181 μmol)was saponified as described above with lithium hydroxide monohydrate (15mg, 360 μmol) to provide 51 mg (71%) of the title compound. UPLC-MS(system 2): t_(r)=1.51 min, m/z (ES+) calculated 399.20 (M+H)⁺, found399.26.

2-((1R,3R)-3-((tert-butoxycarbonyl)(methyl)amino)-4-methyl-1-(prop-2-yn-1-yloxy)pentyl)thiazole-4-carboxylicacid (154): Tubuvaline propargyl ether intermediate 150 (76 mg, 180μmol) was saponified as described above with lithium hydroxidemonohydrate (15 mg, 360 μmol) to provide 50 mg (69%) of the titlecompound. UPLC-MS (system 2): t_(r)=1.47 min, m/z (ES+) calculated397.18 (M+H)⁺, found 397.25.

2-((1R,3R)-1-(benzyloxy)-3-((tert-butoxycarbonyl)(methyl)amino)-4-methylpentyl)thiazole-4-carboxylicacid (155): Tubuvaline benzyl ether intermediate 151 (21 mg, 44 μmol)was saponified as described above with lithium hydroxide monohydrate(5.5 mg, 132 μmol) to provide the title compound. UPLC-MS (system 1):t_(r)=1.72 min, m/z (ES+) calculated 449.21 (M+H)⁺, found 449.18.

General procedure for the amide coupling of O-alkylated tubuvaline freeacids and tubuphenylalanine allyl ester: O-alkylated tubuvaline freeacids 152-155 were pre-activated by dissolution in anhydrousdimethylformamide (25-50 mM) and addition of HATU (2.4 equivalents) andDIPEA (5 equivalents); the mixture was then stirred under nitrogen atroom temperature for 10 minutes. The activated acid was then added tothe known (Org. Lett., 2007, 9, 1605-1607) tubuphenylalanine allyl ester16 and the reaction was then stirred at an ambient temperature undernitrogen, with progress monitored by UPLC/MS. Upon reaction completion,glacial acetic acid (14 equivalents) was then added and the product waspurified by preparative HPLC.

(2S,4R)-allyl4-(2-((1R,3R)-3-((tert-butoxycarbonyl)(methyl)amino)-4-methyl-1-((2-methylallyl)oxy)pentyl)thiazole-4-carboxamido)-2-methyl-5-phenylpentanoate(156): Tubuvaline ether intermediate 152 (114 mg, 277 μmol) was coupledto tubuphenylalanine (Tup) allyl ester 16 (137 mg, 554 μmol) to provide159 mg (90%) of the title compound. UPLC-MS (system 1): t_(r)=1.97 min,m/z (ES+) calculated 642.36 (M+H)⁺, found 642.44.

(2S,4R)-allyl4-(2-((1R,3R)-1-(allyloxy)-3-((tert-butoxycarbonyl)(methyl)amino)-4-methylpentyl)thiazole-4-carboxamido)-2-methyl-5-phenylpentanoate(157): Tubuvaline allyl ether intermediate 153 (44 mg, 100 μmol) wascoupled to tubuphenylalanine (Tup) allyl ester 16 (37 mg, 150 μmol) toprovide 60 mg (95%) of the title compound. UPLC-MS (system 1):t_(r)=2.06 min, m/z (ES+) calculated 628.34 (M+H)⁺, found 628.26.

(2S,4R)-allyl4-(2-((1R,3R)-3-((tert-butoxycarbonyl)(methyl)amino)-4-methyl-1-(prop-2-yn-1-yloxy)pentyl)thiazole-4-carboxamido)-2-methyl-5-phenylpentanoate(158): Tubuvaline propargyl ether intermediate 154 (42 mg, 106 μmol) wascoupled to tubuphenylalanine (Tup) allyl ester 16 (52 mg, 212 μmol) toprovide 48 mg (73%) of the title compound. UPLC-MS (system 2):t_(r)=1.73 min, m/z (ES+) calculated 626.33 (M+H)⁺, found 626.41.

(2S,4R)-allyl4-(2-((1R,3R)-1-(benzyloxy)-3-((tert-butoxycarbonyl)(methyl)amino)-4-methylpentyl)thiazole-4-carboxamido)-2-methyl-5-phenylpentanoate(159): Tubuvaline benzyl ether intermediate 155 (50 mg, 110 μmol) wascoupled to tubuphenylalanine (Tup) allyl ester 16 (60 mg, 165 μmol) toprovide 43 mg (58%) of the title compound. UPLC-MS (system 2):t_(r)=1.93 min, m/z (ES+) calculated 678.36 (M+H)⁺, found 678.45.

General procedure for the Boc deprotection of Tuv(OAlk)-TupIntermediates. O-alkylated tubuvaline-tubuphenylalanine intermediates156-159 were deprotected to reveal the secondary amine functional groupunder acidic conditions with 10% TFA in dichloromethane (25 mM).Specifically, the starting material was dissolved in anhydrousdichloromethane (9 volumes) and stirred under nitrogen at 0 C.Trifluoroacetic acid (1 volume) was then added dropwise to the stirredsolution. The reaction was warmed slowly to room temperature andmonitored by UPLC/MS. Upon completion, the reaction was concentrated byrotary evaporation and pumped down on a vacuum line overnight. The freeamines 160-163 were carried forward without further purification.

(2S,4R)-allyl2-methyl-4-(2-((1R,3R)-4-methyl-1-((2-methylallyl)oxy)-3-(methylamino)pentyl)thiazole-4-carboxamido)-5-phenylpentanoate(160): Boc-protected Tuv-Tup intermediate 156 (159 mg, 248 μmol) wasdeprotected as described above to provide 127 mg (95%) of the titlecompound. UPLC-MS (system 1): t_(r)=1.18 min, m/z (ES+) calculated542.31 (M+H)⁺, found 542.38.

(2S,4R)-allyl4-(2-((1R,3R)-1-(allyloxy)-4-methyl-3-(methylamino)pentyl)thiazole-4-carboxamido)-2-methyl-5-phenylpentanoate(161): Boc-protected Tuv(O-allyl)-Tup intermediate 157 (60 mg, 96 μmol)was deprotected as described above to provide 52 mg (quant.) of thetitle compound. UPLC-MS (system 1): t, =1.16 min, m/z (ES+) calculated528.29 (M+H)⁺, found 528.05.

(2S,4R)-allyl2-methyl-4-(2-((1R,3R)-4-methyl-3-(methylamino)-1-(prop-2-yn-1-yloxy)pentyl)thiazole-4-carboxamido)-5-phenylpentanoate(162): Boc-protected Tuv(O-propargyl)-Tup intermediate 158 (39 mg, 62μmol) was deprotected as described above to provide 45 mg (quant.) ofthe title compound. UPLC-MS (system 2): t_(r)=1.08 min, m/z (ES+)calculated 526.28 (M+H)⁺, found 526.35.

(2S,4R)-allyl4-(2-((1R,3R)-1-(benzyloxy)-4-methyl-3-(methylamino)pentyl)thiazole-4-carboxamido)-2-methyl-5-phenylpentanoate(163): Boc-protected Tuv(O-benzyl)-Tup intermediate 159 (38 mg, 56 μmol)was deprotected as described above to provide the title compound inquantitative yield. UPLC-MS (system 2): t_(r)=1.20 min, m/z (ES+)calculated 578.31 (M+H)⁺, found 578.38.

General procedure for the amide coupling of O-alkylatedtubuvaline-tubuphenylalanine dipeptides with Fmoc-protectedL-isoleucine. Commercially available Fmoc-L-Isoleucine (1.3-2equivalents) was dissolved in anhydrous dimethylformamide (50-200 mM)and pre-activated with HATU (1.5-2 equivalents) and DIPEA (2equivalents); the mixture was stirred for 10 minutes at room temperatureunder nitrogen. The activated acid was then added to theTuv(O-ether)-Tup dipeptides 160-163; the reaction was stirred at roomtemperature under nitrogen and monitored by UPLC/MS. Once the reactionhad stopped progressing or had reached completion, glacial acetic acid(13 equivalents) was added and the reaction was purified by prep HPLC.

(2S,4R)-allyl4-(2-((5S,8R,10R)-5-((S)-sec-butyl)-1-(9H-fluoren-9-yl)-8-isopropyl-7,13-dimethyl-3,6-dioxo-2,11-dioxa-4,7-diazatetradec-13-en-10-yl)thiazole-4-carboxamido)-2-methyl-5-phenylpentanoate(164): Tuv-Tup intermediate 160 (127 mg, 235 μmol) was coupled toFmoc-L-Ile as described above to provide 90 mg (44%) of the titlecompound. UPLC-MS (system 1): t_(r)=2.14 min, m/z (ES+) calculated877.46 (M+H)⁺, found 877.56.

(2S,4R)-allyl4-(2-((5S,8R,10R)-5-((S)-sec-butyl)-1-(9H-fluoren-9-yl)-8-isopropyl-7-methyl-3,6-dioxo-2,11-dioxa-4,7-diazatetradec-13-en-10-yl)thiazole-4-carboxamido)-2-methyl-5-phenylpentanoate(165): Tuv(O-allyl)-Tup intermediate 161 (52 mg, 100 μmol) was coupledto Fmoc-L-Ile as described above to provide 38 mg (44%) of the titlecompound. UPLC-MS (system 2): t_(r)=1.94 min, m/z (ES+) calculated863.44 (M+H)⁺, found 863.54.

(2S,4R)-allyl4-(2-((5S,8R,10R)-5-((S)-sec-butyl)-1-(9H-fluoren-9-yl)-8-isopropyl-7-methyl-3,6-dioxo-2,11-dioxa-4,7-diazatetradec-13-yn-10-yl)thiazole-4-carboxamido)-2-methyl-5-phenylpentanoate(166): Tuv(O-propargyl)-Tup intermediate 162 (62 μmol) was coupled toFmoc-L-Ile as described above to provide 33 mg (62%) of the titlecompound. UPLC-MS (system 2): t_(r)=1.83 min, m/z (ES+) calculated861.43 (M+H)⁺, found 861.53.

(2S,4R)-allyl4-(2-((5S,8R,10R)-5-((S)-sec-butyl)-1-(9H-fluoren-9-yl)-8-isopropyl-7-methyl-3,6-dioxo-12-phenyl-2,11-dioxa-4,7-diazadodecan-10-yl)thiazole-4-carboxamido)-2-methyl-5-phenylpentanoate(167): Tuv(O-benzyl)-Tup intermediate 163 (56 μmol) was coupled toFmoc-L-Ile as described above to provide 23 mg (45%) of the titlecompound. UPLC-MS (system 2): t_(r)=2.04 min, m/z (ES+) calculated913.46 (M+H)⁺, found 913.56.

General procedure for the Fmoc-deprotection of isoleucine-O-alkylatedtubuvaline-tubuphenylalanine tripeptides: Fmoc-le-Tuv(O-ether)-Tup allylester (164-167) was treated with 20% piperidine in dimethylformamide (20mM), with stirring under nitrogen at room temperature. Once completedeprotection had been achieved, as monitored by UPLC/MS, the reactionmixture was concentrated by rotary evaporation. The crude product wasthen purified by preparative HPLC to provide free amine tripeptides168-171.

(2S,4R)-allyl4-(2-((1R,3R)-3-((2S,3S)-2-amino-N,3-dimethylpentanamido)-4-methyl-1-((2-methylallyl)oxy)pentyl)thiazole-4-carboxamido)-2-methyl-5-phenylpentanoate(168): Fmoc-Ile-Tuv-Tup intermediate 164 (90 mg, 103 μmol) wasdeprotected as described above to provide 29 mg (43%) of the titlecompound. UPLC-MS (system 1): t_(r)=1.29 min, m/z (ES+) calculated655.39 (M+H)⁺, found 655.48.

(2S,4R)-allyl4-(2-((1R,3R)-1-(allyloxy)-3-((2S,3S)-2-amino-N,3-dimethylpentanamido)-4-methylpentyl)thiazole-4-carboxamido)-2-methyl-5-phenylpentanoate(169): Fmoc-Ile-Tuv(O-allyl)-Tup intermediate 165 (38 mg, 44 μmol) wasdeprotected as described above to provide 25 mg (89%) of the titlecompound. UPLC-MS (system 2): t_(r)=1.20 min, m/z (ES+) calculated641.38 (M+H)⁺, found 641.46.

(2S,4R)-allyl4-(2-((1R,3R)-3-((2S,3S)-2-amino-N,3-dimethylpentanamido)-4-methyl-1-(prop-2-yn-1-yloxy)pentyl)thiazole-4-carboxamido)-2-methyl-5-phenylpentanoate(170): Fmoc-Ile-Tuv(O-propargyl)-Tup intermediate 166 (33 mg, 38 μmol)was deprotected as described above to provide 25 mg (quant.) of thetitle compound. UPLC-MS (system 2): t_(r)=1.15 min, m/z (ES+) calculated639.36 (M+H)⁺, found 639.44.

(2S,4R)-allyl4-(2-((1R,3R)-3-((2S,3S)-2-amino-N,3-dimethylpentanamido)-1-(benzyloxy)-4-methylpentyl)thiazole-4-carboxamido)-2-methyl-5-phenylpentanoate(171): Fmoc-Ile-Tuv(O-benzyl)-Tup intermediate 167 (23 mg, 25 μmol) wasdeprotected as described above to provide the title compound inquantitative yield. UPLC-MS (system 2): t_(r)=1.30 min. m/z (ES+)calculated 691.39 (M+H)⁺, found 691.48.

General procedure for the amide coupling ofisoleucine-tubuvaline(ether)-tubuphenylalanine tripeptides with(R)—N-methyl-pipecolic acid: Commercially available(R)—N-methyl-pipecolic acid (D-Mep) 36 (1.5-2 equivalents) was dissolvedin anhydrous dimethylformamide (25-50 mM) and pre-activated with HATU (2equivalents) and DIPEA (4 equivalents); the mixture was stirred for 10minutes at room temperature under nitrogen. The activated acid was thenadded to the Ile-Tuv(O-ether)-Tup tripeptides 168-171; the reaction wasstirred at room temperature under nitrogen and monitored by UPLC/MS.Upon reaction completion, glacial acetic acid (14 equivalents) was thenadded and the product was purified by preparative HPLC.

(2S,4R)-allyl4-(2-((1R,3R)-3-((2S,3S)—N,3-dimethyl-2-((R)-1-methylpiperidine-2-carboxamido)pentanamido)-4-methyl-1-((2-methylallyl)oxy)pentyl)thiazole-4-carboxamido)-2-methyl-5-phenylpentanoate(172): Ile-Tuv-Tup intermediate 168 (55 mg, 84 μmol) was coupled toD-Mep 36 as described above to provide 40 mg (62%) of the titlecompound. UPLC-MS (system 1): t_(r)=1.27 min, m/z (ES+) calculated780.48 (M+H)⁺, found 780.58.

(2S,4R)-allyl4-(2-((1R,3R)-1-(allyloxy)-3-((2S,3S)—N,3-dimethyl-2-((R)-1-methylpiperidine-2-carboxamido)pentanamido)-4-methylpentyl)thiazole-4-carboxamido)-2-methyl-5-phenylpentanoate(173): Ile-Tuv(O-allyl)-Tup intermediate 169 (5 mg, 7.8 μmol was coupledto D-Mep 36 as described above to provide 6 mg (quant.) of the titlecompound. UPLC-MS (system 2): t_(r)=1.28 min, m/z (ES+) calculated766.46 (M+H)⁺, found 766.54.

(2S,4R)-allyl4-(2-((1R,3R)-3-((2S,3S)—N,3-dimethyl-2-((R)-1-methylpiperidine-2-carboxamido)pentanamido)-4-methyl-1-(prop-2-yn-1-yloxy)pentyl)thiazole-4-carboxamido)-2-methyl-5-phenylpentanoate(174): Ile-Tuv(O-propargyl)-Tup intermediate 170 (18 mg, 28 μmol) wascoupled to D-Mep 36 as described above to provide 20 mg (93%) of thetitle compound. UPLC-MS (system 2): t, =1.23 min, m/z (ES+) calculated764.44 (M+H)^(t), found 764.53.

(2S,4R)-allyl4-(2-((1R,3R)-1-(benzyloxy)-3-((2S,3S)—N,3-dimethyl-2-((R)-1-methylpiperidine-2-carboxamido)pentanamido)-4-methylpentyl)thiazole-4-carboxamido)-2-methyl-5-phenylpentanoate(175): Ile-Tuv(O-benzyl)-Tup intermediate 171 (5 mg, 7 μmol) was coupledto D-Mep 36 as described above to provide 4.4 mg (75%) of the titlecompound. UPLC-MS (system 1): t_(r)=1.42 min, m/z (ES+) calculated816.48 (M+H)⁺, found 816.64.

General procedure for the allyl ester removal from D-methylpipecolicacid-isoleucine-tubuvaline(ether)-tubuphenylalanine tubulysinintermediates: Allyl ester-protected tubulysin ether intermediate(172-175) was dissolved in anhydrous dichloromethane (20 mM) treatedwith palladium tetrakis(triphenylphosphine) (0.1 equiv.),triphenylphosphine (0.2 equivalents), and anhydrous pyrrolidine (8equivalents), and the reaction was stirred at an ambient temperatureunder nitrogen. Once UPLC/MS revealed conversion to the product freeacid, the reaction was quenched with glacial acetic acid (22equivalents), diluted with acetonitrile and dimethylformamide, and thenconcentrated by rotary evaporation. The crude tubulysin ether was thenpurified by preparative HPLC.

(2S,4R)-4-(2-((1R,3R)-3-((2S,3S)—N,3-dimethyl-2-((R)-1-methylpiperidine-2-carboxamido)pentanamido)-4-methyl-1-((2-methylallyl)oxy)pentyl)thiazole-4-carboxamido)-2-methyl-5-phenylpentanoicacid (176): Allyl ester-protected tubulysin methylallyl etherintermediate 172 (19 mg, 24 μmol) was deprotected as described above toprovide 14 mg (93%) of tubulysin ether 176. UPLC-MS (system 2):t_(r)=1.16 min, m/z (ES+) calculated 740.44 (M+H)⁺, found 740.54.

(2S,4R)-4-(2-((1R,3R)-1-(allyloxy)-3-((2S,3S)—N,3-dimethyl-2-((R)-1-methylpiperidine-2-carboxamido)pentanamido)-4-methylpentyl)thiazole-4-carboxamido)-2-methyl-5-phenylpentanoicacid (177): Allyl ester-protected tubulysin allyl ether intermediate 173(7 mg, 9 μmol) was deprotected as described above to provide 6 mg (92%)of tubulysin allyl ether 177. UPLC-MS (system 1): t_(r)=1.20 min, m/z(ES+) calculated 726.43 (M+H)⁺, found 726.33.

(2S,4R)-4-(2-((1R,3R)-3-((2S,3S)—N,3-dimethyl-2-((R)-1-methylpiperidine-2-carboxamido)pentanamido)-4-methyl-1-(prop-2-yn-1-yloxy)pentyl)thiazole-4-carboxamido)-2-methyl-5-phenylpentanoicacid (178): Allyl ester-protected tubulysin propargyl ether intermediate174 (5.2 mg, 6.8 μmol) was deprotected as described above to provide 2.7mg (55%) of tubulysin propargyl ether 178. UPLC-MS (system 2):t_(r)=1.09 min, z/z (ES+) calculated 724.41 (M+H)⁺, found 724.50.

(2S,4R)-4-(2-((1R,3R)-1-(benzyloxy)-3-((2S,3S)—N,3-dimethyl-2-((R)-1-methylpiperidine-2-carboxamido)pentanamido)-4-methylpentyl)thiazole-4-carboxamido)-2-methyl-5-phenylpentanoicacid (179): Allyl ester-protected tubulysin benzyl ether intermediate175 (5 mg, 6 μmol) was deprotected as described above to provide 4.5 mg(96%) of tubulysin benzyl ether 179. UPLC-MS (system 1): 1, 1.26 min,m/z (ES+) calculated 776.44 (M+H)⁺, found 776.58.

(2R)-1-(3-(3-((((9H-fluoren-9-yl)methoxy)carbonyl)amino)propanamido)-4-(((2S,3R,4S,5S,6S)-6-((allyloxy)carbonyl)-3,4,5-trihydroxytetrahydro-2H-pyran-2-yl)oxy)benzyl)-2-(((2S,3S)-1-(((1R,3R)-1-(4-(((2R,4S)-5-(allyloxy)-4-methyl-5-oxo-1-phenylpentan-2-yl)carbamoyl)thiazol-2-yl)-4-methyl-1-((2-methylallyl)oxy)pentan-3-ylmethyl)amino)-3-methyl-1-oxopentan-2-yl)carbamoyl)-1-methylpiperidin-1-ium(180). To a flask charged with H-Ile-Tuv(O-methylpropene)-Tup-OAllyl(168, 24 mg, 31 μmol) was added Fmoc-Gluc(Allyl)Q-Mep-OH (78, 28 mg, 31μmol) and HATU (18 mg, 45 μmol) as solids followed by THF (1.2 mL).N,N-Diisopropylethylamine (19 μL, 109 μmol) was added and the reactionwas stirred at room temperature for 1 hour. The reaction was then takenup in DMSO and purified by preparative LC to provide 180 (21 mg, 49%).Analytical UPLC-MS (system 2): t_(r)=1.46 min, m/z (ES+) calculated1410.69 (M)⁺, found 1410.84.

(2R)-1-(3-(3-aminopropanamido)-4-(((2S,3R,4S,5S,6S)-6-carboxy-3,4,5-trihydroxytetrahydro-2H-pyran-2-yl)oxy)benzyl)-2-(((2S,3S)-1-(((1R,3R)-1-(4-(((2R,4S)-4-carboxy-1-phenylpentan-2-yl)carbamoyl)thiazol-2-yl)-4-methyl-1-((2-methylallyl)oxy)pentan-3-yl)(methyl)amino)-3-methyl-1-oxopentan-2-yl)carbamoyl)-1-methylpiperidin-1-ium(181). Fmoc-GlucQ-Tub(O-methylpropene)-OAllyl 180 (12 mg, 8 μmol) wasdeprotected as above (see: General procedure for global deprotection ofFmoc-GlucQ-Tub(OR)-OAllyl) to provide 181 (8.6 mg, 97%). AnalyticalUPLC-MS (system 1): t_(r)=1.02 min, m/z (ES+) calculated 1108.56 (M)⁺,found 1108.69.

(2R)-1-(3-((S)-44-((((9H-fluoren-9-yl)methoxy)carbonyl)amino)-38,45-dioxo-2,5,8,11,14,17,20,23,26,29,32,35-dodecaoxa-39,46-diazanonatetracontanamido)-4-(((2S,3R,4S,5S,6S)-6-carboxy-3,4,5-trihydroxytetrahydro-2H-pyran-2-yl)oxy)benzyl)-2-(((2S,3S)-1-(((1R,3R)-1-(4-(((2R,4S)-4-carboxy-1-phenylpentan-2-yl)carbamoyl)thiazol-2-yl)-4-methyl-1-((2-methylallyl)oxy)pentan-3-yl)(methyl)amino)-3-methyl-1-oxopentan-2-yl)carbamoyl)-1-methylpiperidin-1-ium(182). H-GlucQ-Tub(O-methylpropene) 181 (12.5 mg, 11 μmol) was coupledto Fmoc-Lys(PEG12)-OSu 59 (14 mg, 13.5 μmol) as above (see: Generalprocedure for coupling of H-GlucQ-Tub(OR) to Fmoc-Lys(PEG12)-OSu) toprovide 182 (13 mg, 56%). Analytical UPLC-MS (system 2): t_(r)=1.32 min,m/z (ES+) calculated 2029.05 (M)⁺, found 2029.24.

(2R)-1-(3-((S)-44-amino-38,45-dioxo-2,5,8,11,14,17,20,23,26,29,32,35-dodecaoxa-39,46-diazanonatetracontanamido)-4-(((2S,3R,4S,5S,6S)-6-carboxy-3,4,5-trihydroxytetrahydro-2H-pyran-2-yl)oxy)benzyl)-2-(((2S,3S)-1-(((1R,3R)-1-(4-(((2R,4S)-4-carboxy-1-phenylpentan-2-yl)carbamoyl)thiazol-2-yl)-4-methyl-1-((2-methylallyl)oxy)pentan-3-yl)(methyl)amino)-3-methyl-1-oxopentan-2-yl)carbamoyl)-1-methylpiperidin-1-ium(183). Fmoc-Lys(PEG12)-GlucQ-Tub(O-methylpropene) 182 (13 mg, 6 μmol)was deprotected as above (see: General procedure deprotection ofFmoc-Lys(PEG12)-GlucQ-Tub(OR)) to provide 183 (11 mg, quant.).Analytical UPLC-MS (system 2): t_(r)=1.04 min, m/z (ES+) calculated1806.98 (M)⁺, found 1807.16.

(2R)-1-(3-((S)-44-((S)-3-((tert-butoxycarbonyl)amino)-2-(2,5-dioxo-2,5-dihydro-1H-pyrrol-1-yl)propanamido)-38,45-dioxo-2,5,8,11,14,17,20,23,26,29,32,35-dodecaoxa-39,46-diazanonatetracontanamido)-4-(((2S,3R,4S,5S,6S)-6-carboxy-3,4,5-trihydroxytetrahydro-2H-pyran-2-yl)oxy)benzyl)-2-(((2S,3S)-1-(((1R,3R)-1-(4-(((2R,4S)-4-carboxy-1-phenylpentan-2-yl)carbamoyl)thiazol-2-yl)-4-methyl-1-((2-methylallyl)oxy)pentan-3-yl)(methyl)amino)-3-methyl-1-oxopentan-2-yl)carbamoyl)-1-methylpiperidin-1-ium(184). H-Lys(PEG12)-GlucQ-Tub(O-methylpropene) 183 (11.5 mg, 6.4 μmol)was coupled to mDPR-OPFP 44 (4.3 mg, 9.5 μmol) as above (see: Generalprocedure for coupling H-Lys(PEG12)-GlucQ-Tub(OR) to mDPR-OPFP) toprovide 184 (8.3 mg, 63%). Analytical UPLC-MS (system 2): t_(r)=1.24min, m/z (ES+) calculated 2073.07 (M), found 2073.25.

(2R)-1-(3-((S)-44-((S)-3-amino-2-(2,5-dioxo-2,5-dihydro-1H-pyrrol-1-yl)propanamido)-38,45-dioxo-2,5,8,11,14,17,20,23,26,29,32,35-dodecaoxa-39,46-diazanonatetracontanamido)-4-(((2S,3R,4S,5S,6S)-6-carboxy-3,4,5-trihydroxytetrahydro-2H-pyran-2-yl)oxy)benzyl)-2-(((2S,3S)-1-(((1R,3R)-1-(4-(((2R,4S)-4-carboxy-1-phenylpentan-2-yl)carbamoyl)thiazol-2-yl)-4-methyl-1-((2-methylallyl)oxy)pentan-3-yl)(methyl)amino)-3-methyl-1-oxopentan-2-yl)carbamoyl)-1-methylpiperidin-1-ium(185). mDPR(Boc)-Lys(PEG12)-GlucQ-Tub(O-methylpropene) 184 (8.3 mg, 4μmol) was deprotected as above (see: General procedure for deprotectionof mDPR(Boc)-Lys(PEG12)-GlucQ-Tub(OR)) to provide 185 (7.4 mg, 94%).Analytical UPLC-MS (system 2): t_(r)=1.05 min, m/z (ES+) calculated1973.02 (M)⁺, found 1973.21.

Solid Phase Synthesis of TubOEt Analogues Replacing Tubulysin Ile orD-Mep Residues:

2-((1R,3R)-3-((((9H-fluoren-9-yl)methoxy)carbonyl)(methyl)amino)-1-,ethoxy-4-methylpentyl)thiazole-4-carboxylic acid (200): A vial wascharged with Boc-MeN-TuvOEt-COOH (22, 153 mg, 0.40 mmol) and dissolvedin anhydrous DCM (4 mL). The solution was cooled to 0° C., then TFA(0.40 mL, 5.22 mmol) was added dropwise. Following the TFA addition thereaction was allowed to slowly warm to room temperature. After 4 hcomplete removal of the Boc protecting group was observed. The reactionwas diluted with 5 mL of toluene and concentrated to dryness. Theintermediate amine was used without further purification. AnalyticalUPLC-MS (system 1): t_(r)=0.86 min, m/z (ES+) calculated 287.1 (M+H)⁺,found 287.2. The intermediate amine-trifluoroacetic acid salt wasdissolved in 1,4-dioxane (2.0 mL), then water (2.0 mL) and DIPEA (0.41mL, 2.4 mmol) were added. A solution of FmocCl (122 mg, 0.47 mmol) in1,4-dioxane was then added dropwise. After 8 h the reaction was dilutedwith 10% DMSO in MeCN and purified by preparative HPLC to provideFmocMeN-TuvOEt-COOH (200, 88 mg, 44%). Analytical UPLC-MS (system 1):t_(r)=2.35 min, m/z (ES+) calculated 509.2 (M+H)⁺, found 509.2;calculated 531.2 (M+Na)⁺, found 531.1

(2S,4R)-4-(2-((1R,3R)-3-((((9H-fluoren-9-yl)methoxy)carbonyl)(methyl)-amino)-1-ethoxy-4-methylpentyl)thiazole-4-carboxamido)-2-methyl-5-phenylpentanoicacid (202): FmocMeN-TuvOEt-COOH (200, 80 mg, 0.16 mmol) was dissolved inanhydrous DMF (0.8 mL) and then a solution HATU (60 mg, 0.16 mmol) inanhydrous DMF (0.8 mL) was added, followed by DIPEA (0.21 mL, 1.2 mmol).After 5 min the hydrochloride salt of(2S,4R)-4-amino-2-methyl-5-phenylpentanoic acid (201, HCl.Tup-COOH, 96mg, 0.39 mmol) was added in one portion. The reaction was stirred for 5h at room temperature, then diluted with 10% DMSO in MeCN and purifiedby preparative HPLC to provide FmocMeN-TuvOEt-Tup-COOH (202.95 mg, 87%).Analytical UPLC-MS (system 1): t_(r)=2.40 min, m/z (ES+) calculated698.3 (M+H)⁺, found 698.3.

General Procedure for Chlorotrityl Lantern Loading: Six SynPhase™polyacrylamide series-D lanterns functionalized with a trityl alcohollinker and a nominal loading of 8 μmol (Mimotopes, Victoria. Australia)were placed in a dry vial and converted to the trityl chloride linker bytreatment with 3 mL of a 10% AcCl in anhydrous DCM solution. After 3 hof gentle swirling at room temperature the solution was removed and thelanterns were washed 3 times with 5 mL of anhydrous DCM. Next, asolution of 202 (57 mg, 81.7 μmol) and DIPEA (57 μL, 327 μmol) in 3 mLof anhydrous DCM was added to the lanterns. After 5 h of gentle swirlingat room temperature the solution was removed from the lanterns and thelanterns were washed 3 times with 5 mL of DMF, 3 times with 5 mL of DCM,then dried overnight under a stream of argon to obtain lanterns loadedwith FmocMeN-TuvOEt-Tup.

General Procedure for the Preparation of Ile replacement Analogues ofTubOEt (203-215): Step 1: Fmoc Removal. A lantern loaded withFmocMeN-TuvOEt-Tup as prepared above was treated with 1 mL of 20%piperidine in DMF for 30 min. The solution was removed and the lanternwas then washed 3 times with 1.5 mL of DMF. Step 2: Amino Acid Coupling.In a separate vial 0.5 mL of a 240 mM solution of the appropriateFmoc-protected amino acid (FmocHN-Xxx-COOH) in DMF and 0.5 mL of a 200mM solution of HATU in DMF were combined and DIPEA (45 μL, 0.24 mmol)was added. After 2 min the activated amino acid solution was added tothe lantern and gently stirred for 2 h. The lantern was treated a secondtime with the activated Fmoc amino acid solution for 2 h. The solutionwas then removed and the lantern was washed 3 times with 1.5 mL DMF.Step 3: Fmoc Removal. The lantern loaded with FmocHNXxx-TuvOEt-Tup wastreated with 1 mL of 20% piperidine in DMF for 30 min. The solution wasremoved, and then the lantern was washed 3 times with 1.5 mL of DMF.Step 4: Mep Coupling. In a separate vial 0.5 mL of a 240 mM solution of(R)-1-methylpiperidine-2-carboxylic acid (Mep) in DMF and 0.5 ml, of a200 mM solution of HATU in DMF were combined, and DIPEA (45 μL, 0.24mmol) was added. After 2 min the activated Mep solution was added to thelantern and gently stirred for 1.5 h. The solution was removed and thelantern was then washed 3 times with 1.5 mL DMF and 3 times with 1.5 ml,of DCM. Step 5: Cleavage from the Lantern. Each lantern was treated for90 min with a 20% HFIP solution in DCM. The solution was removed and thelantern was washed with an additional 0.5 ml of 20% HFIP in DCM. Thecombined solutions were filtered through a 45 micron syringe filter andconcentrated to dryness to provide analogues 203-215 (shown immediatelybelow). The analogues were obtained in >85% purity based on UPLC-MSanalysis and the diode array chromatogram.

(2S,4R)-4-(2-((1R,3R)-1-ethoxy-3-((S)-3-ethyl-N-methyl-2-((R)-1-methylpiperidine-2-carboxamido)pentanamido)-4-methylpentyl)thiazole-4-carboxamido)-2-methyl-5-phenylpentanoicacid (203): The TubOEt analogue at the Ile position was preparedaccording to the general method described above, employing(S)-2-((((9H-fluoren-9-yl)methoxy)carbonyl)amino)-3-ethylpentanoic acidin Step 2, to provide 203 (1.17 mg). Analytical UPLC-MS (system 1):t_(r)=1.77 min, m/z (ES+) calculated 728.4 (M+H)⁺, found 728.4.

(2S,4R)-4-(2-((1R,3R)-3-((S)-2-cyclopentyl-N-methyl-2-((R)-1-methylpiperidine-2-carboxamido)acetamido)-1-ethoxy-4-methylpentyl)thiazole-4-carboxamido)-2-methyl-5-phenylpentanoicacid (204): The TubOEt analogue at the Ile position was preparedaccording to the general method described above, employing(S)-2-((((9H-fluoren-9-yl)methoxy)carbonyl)amino)-2-cyclopentylaceticacid in Step 2, to provide 204 (1.71 mg). Analytical UPLC-MS (system 1):t_(r)=1.72 min, m/z (ES+) calculated 726.4 (M+H)⁺, found 726.4.

(2S,4R)-4-(2-((1R,3R)-3-((S)-2-cyclohexyl-N-methyl-2-((R)-1-methylpiperidine-2-carboxamido)acetamido)-1-ethoxy-4-methylpentyl)thiazole-4-carboxamido)-2-methyl-5-phenylpentanoicacid (205): The TubOEt analogue at the Ile position was preparedaccording to the general method described above, employing(S)-2-((((9H-fluoren-9-yl)methoxy)carbonyl)amino)-2-cyclohexylaceticacid in Step 2, to provide 205 (1.59 mg). Analytical UPLC-MS (system 1):1, =1.77 min, m/z (ES+) calculated 740.4 (M+H)⁺, found 740.4.

(2S,4R)-4-(2-((1R,3R)-1-ethoxy-3-((2S,3S)-3-methoxy-N-methyl-2-((R)-1-methylpiperidine-2-carboxamido)butanamido)-4-methylpentyl)thiazole-4-carboxamido)-2-methyl-5-phenylpentanoicacid (206): The TubOEt analogue at the Ile position was preparedaccording to the general method described above, employingN-(((9H-fluoren-9-yl)methoxy)carbonyl)-O-methyl-L-allothreonine in Step2, to provide 206 (1.50 mg). Analytical UPLC-MS (system 1): t_(r)=1.58min, m/z (ES+) calculated 716.4 (M+H)⁺, found 716.4.

(2S,4R)-4-(2-((1R,3R)-1-ethoxy-3-((2S,3R)-3-methoxy-N-methyl-2-((R)-1-methylpiperidine-2-carboxamido)butanamido)-4-methylpentyl)thiazole-4-carboxamido)-2-methyl-5-phenylpentanoicacid (207): The TubOEt analogue at the Ile position was preparedaccording to the general method described above, employingN-(((9H-fluoren-9-yl)methoxy)carbonyl)-O-methyl-L-threonine in Step 2,to provide 207 (1.44 mg). Analytical UPLC-MS (system 1): t_(r)=1.59 min,m/z (ES+) calculated 716.4 (M+H)⁺, found 716.4.

(2S,4R)-4-(2-((1R,3R)-3-((S)-2-(2,3-dihydro-1H-inden-2-yl)-N-methyl-2-((R)-1-methylpiperidine-2-carboxamido)acetamido)-1-ethoxy-4-methylpentyl)thiazole-4-carboxamido)-2-methyl-5-phenylpentanoicacid (208): The TubOEt analogue at the Ile position was preparedaccording to the general method described above, employing(S)-2-((((9H-fluoren-9-yl)methoxy)carbonyl)amino)-2-(2,3-dihydro-1H-inden-2-yl)aceticacid in Step 2, to provide 208 (1.15 mg). Analytical UPLC-MS (system 1):t_(r)=1.84 min, m/z (ES+) calculated 774.4 (M+H)⁺, found 774.4.

(2S,4R)-4-(2-((1R,3R)-3-((2S,3R)—N,3-dimethyl-2-((R)-1-methylpiperidine-2-carboxamido)pentanamido)-1-ethoxy-4-methylpentyl)thiazole-4-carboxamido)-2-methyl-5-phenylpentanoicacid (209): The TubOEt analogue at the lie position was preparedaccording to the general method described above, employing(((9H-fluoren-9-yl)methoxy)carbonyl)-L-alloisoleucine in Step 2, toprovide 209 (1.33 mg). Analytical UPLC-MS (system 1): t_(r)=1.78 min,m/z (ES+) calculated 714.4 (M+H)⁺, found 714.4.

(2S,4R)-4-(2-((1R,3R)-1-ethoxy-4-methyl-3-((S)—N-methyl-2-((R)-1-methylpiperidine-2-carboxamido)-2-(tetrahydro-2H-pyran-4-yl)acetamido)pentyl)thiazole-4-carboxamido)-2-methyl-5-phenylpentanoicacid (210): The TubOEt analogue at the Ile position was preparedaccording to the general method described above, employing(S)-2-((((9H-fluoren-9-yl)methoxy)carbonyl)amino)-2-(tetrahydro-2H-pyran-4-yl)aceticacid in Step 2, to provide 210 (1.07 mg). Analytical UPLC-MS (system 1):t_(r)=1.20 min, m/z (ES+) calculated 742.4 (M+H)⁺, found 742.4.

(2S,4R)-4-(2-((1R,3R)-1-ethoxy-3-(2-(3-fluorobicyclo[1.1.1]pentan-1-yl)-N-methyl-2-((R)-1-methylpiperidine-2-carboxamido)acetamido)-4-methylpentyl)thiazole-4-carboxamido)-2-methyl-5-phenylpentanoicacid (211): The TubOEt analogue at the Ile position was preparedaccording to the general method described above, employing racemic2-((((9H-fluoren-9-yl)methoxy)carbonyl)amino)-2-(3-fluorobicyclo[1.1.1]pentan-1-yl)aceticacid in Step 2, to provide 211 (2.69 mg) as a mixture of epimers.Analytical UPLC-MS (system 1): Epimer 1: t_(r)=1.67 min, m/z (ES+)calculated 742.4 (M+H)⁺, found 742.3; Epimer 2: t_(r)=1.83 min, m/z(ES+) calculated 742.4 (M+H)⁺, found 742.3.

(2S,4R)-4-(2-((1R,3R)-3-((S)-3-cyclopropyl-N-methyl-2-((R)-1-methylpiperidine-2-carboxamido)propanamido)-1-ethoxy-4-methylpentyl)thiazole-4-carboxamido)-2-methyl-5-phenylpentanoicacid (212): The TubOEt analogue at the Ile position was preparedaccording to the general method described above, employing(S)-2-((((9H-fluoren-9-yl)methoxy)carbonyl)amino)-3-cyclopropylpropanoicacid in Step 2, to provide 212 (3.21 mg). Analytical UPLC-MS (system 1):t_(r)=1.66 min, m/z (ES+) calculated 712.4 (M+H)⁺, found 712.3.

(2S,4R)-4-(2-((1R,3R)-3-((S)-3-cyclohexyl-N-methyl-2-((R)-1-methylpiperidine-2-carboxamido)propanamido)-1-ethoxy-4-methylpentyl)thiazole-4-carboxamido)-2-methyl-5-phenylpentanoicacid (213): The TubOEt analogue at the Ile position was preparedaccording to the general method described above, employing(S)-2-((((91-fluoren-9-yl)methoxy)carbonyl)amino)-3-cyclohexylpropanoicacid in Step 2, to provide 213 (1.72 mg). Analytical UPLC-MS (system 1):t_(r)=1.87 min, m/z (ES+) calculated 754.5 (M+H)_(, found) 754.4.

(2S,4R)-4-(2-((1R,3R)-3-((2S,3S)-3-(tert-butoxy)-N-methyl-2-((R)-1-methylpiperidine-2-carboxamido)butanamido)-1-ethoxy-4-methylpentyl)thiazole-4-carboxamido)-2-methyl-5-phenylpentanoicacid (214): The TubOEt analogue at the Ile position was preparedaccording to the general method described above, employingN-(((9H-fluoren-9-yl)methoxy)carbonyl)-O-(tert-butyl)-L-allothreonine inStep 2, to provide 214 (2.31 mg). Analytical UPLC-MS (system 1):t_(r)=1.77 min, m/z (ES+) calculated 758.5 (M+H)⁺, found 758.4.

(2S,4R)-4-(2-((1R,3R)-3-((2S,3R)-3-(tert-butoxy)-N-methyl-2-((R)-1-methylpiperidine-2-carboxamido)butanamido)-1-ethoxy-4-methylpentyl)thiazole-4-carboxamido)-2-methyl-5-phenylpentanoicacid (215): The TubOEt analogue at the Ile position was preparedaccording to the general method described above, employingN-(((9H-fluoren-9-yl)methoxy)carbonyl)-O-(tert-butyl)-L-threonine inStep 2, to provide 215 (2.35 mg). Analytical UPLC-MS (system 1):t_(r)=1.76 min, m/z (ES+) calculated 758.5 (M+H)⁺, found 758.4.

General Procedure for the Preparation of D-Mep Replacement Analogues ofTubOEt: Step 1: Fmoc Removal. A lantern loaded with Fmoc-MeN-TuvOEt-Tupas described above was treated with 1 mL of 20% piperidine in DMF for 30min. The solution was removed and the lantern was then washed 3 timeswith 1.5 mL of DMF. Step 2: Amino Acid Coupling. In a separate vial 0.5mL of a 240 mM solution of FmocHN-Ile-COOH in DMF and 0.5 mL of a 200 mMsolution of HATU in DMF were combined and DIPEA (45 μL, 0.24 mmol) wasadded. After 2 min the activated Fmoc-Ile solution was added to thelantern and gently stirred for 2 h. The lantern was treated a secondtime with the activated Fmoc-Ile amino acid solution for 2 h. Thesolution was then removed and the lantern was washed 3 times with 1.5 mLDMF. Step 3: Fmoc Removal. The lantern loaded with FmocHN-Ile-TuvOEt-Tupwas treated with 1 mL of 20% piperidine in DMF for 30 min. The solutionwas removed and the lantern was washed 3 times with 1.5 mL of DMF. Step4: Mep analogue Coupling. In a separate vial 0.5 mL of a 240 mM solutionof the appropriate Mep analogue in DMF and 0.5 mL of a 200 mM solutionof HATU in DMF were combined, and DIPEA (45μ, 0.24 mmol) was added.After 2 min, the activated Mep analogue solution was added to thelantern and gently stirred for 2 h. The lantern was treated a secondtime with the activated Mep analogue solution for 2 h. The solution wasremoved and the lantern was washed 3 times with 1.5 mL DMF and thenwashed 3 times with 1.5 mL of DCM. Step 5: Cleavage from the Lantern.Each lantern was treated for 90 min with a 20% HFIP solution in DCM. Thesolution was removed and the lantern was washed with an additional 0.5mL of 20% HFIP in DCM. The combined solutions were filtered through a 45micron syringe filter and concentrated to dryness to provide analogues216-221 (shown immediately below). The analogues were obtained in >85%purity based on UPLC-MS analysis and the diode array chromatogram.

General procedure for the N-methylation of D-Mep analogues (224-227).Commercially available pipecolic acid analogues (cf. 222, 0.30 mmol)were dissolved in a mixture of 0.4 mL of methanol and a solution of 37%formaldehyde in water (0.23 mL, 3.0 mmol). Pd/C (10 wt. %, 10 mg) wasadded, the flask was equipped with a hydrogen-filled balloon, and thereactions were stirred overnight. The Pd was removed by filteringthrough a plug of Celite and concentrated by rotary evaporation. Theresidue obtained was concentrated from 2.0 mL of methanol 5 additionaltimes to obtain the desired N-methylated pipecolic acid analogues224-227.

5,5-difluoro-1-methylpiperidine-2-carboxylic acid (224):5,5-difluoropiperidine-2-carboxylic acid (50 mg, 0.30 mmol wasmethylated using the procedure described above to provide5,5-difluoro-1-methylpiperidine-2-carboxylic acid (224, 47 mg, 87%).Analytical UPLC-MS (system 1): t_(r)=0.32 min, m/z (ES+) calculated180.1 (M+H)⁺, found 180.0.

2-methyl-2-azabicyclo[3.1.1]heptane-1-carboxylic acid (225):2-azabicyclo[3.1.1]heptane-1-carboxylic acid hydrochloride (53 mg, 0.30mmol) was methylated using the procedure described above to provide2-methyl-2-azabicyclo[3.1.1]heptane-1-carboxylic acid (225, 60 mg,quantitative yield). Analytical UPLC-MS (system 1): t_(r)=0.39 min, m/z(ES+) calculated 156.1 (M+H)⁺. found 156.1.

(1S,3R,4S)-2-methyl-2-azabicyclo[2.2.2]octane-3-carboxylic acid (226):(1S,3R,4S)-2-azabicyclo[2.2.2]octane-3-carboxylic acid (47 mg, 0.30mmol) was methylated using the procedure described above to provide(1S,3R,4S)-2-methyl-2-azabicyclo[2.2.2]octane-3-carboxylic acid (226, 53mg, quantitative yield). Analytical UPLC-MS (system 1): t_(r)=0.40 min,m/z (ES+) calculated 170.1 (M+H)⁺, found 170.0.

(1S,3R,4R)-2-methyl-2-azabicyclo[2.2.1]heptane-3-carboxylic acid (227):(1S,3R,4R)-2-(tert-butoxycarbonyl)-2-azabicyclo[2.2.1]heptane-3-carboxylicacid (73 mg, 0.30 mmol) was dissolved in 1.0 mL of DCM, then 0.30 mL ofTFA was added and the reaction was stirred for 1.5 h to remove the Bocprotecting group. The reaction was diluted with 3 mL of toluene andconcentrated to dryness to afford(1S,3R,4R)-2-azabicyclo[2.2.1]heptane-3-carboxylic acid. AnalyticalUPLC-MS (system 1): t_(r)=0.85 min, m/z (ES+) calculated 142.1 (M+H)⁺.found 142.1. The intermediate(1S,3R,4R)-2-azabicyclo[2.2.1]heptane-3-carboxylic acid was thenmethylated using the procedure described above to provide thetrifluoroacetic acid salt of (IS,3R,4R)-2-methyl-2-azabicyclo[2.2.1]heptane-3-carboxylic acid (227, 66mg, 83%). Analytical UPLC-MS (system 1): t_(r)=0.89 min, m/z (ES+)calculated 156.1 (M+H)⁺, found 156.1

(2S,4R)-4-(2-((1R,3R)-3-((2S,3S)-2-(5,5-difluoro-1-methylpiperidine-2-carboxamido)-N,3-dimethylpentanamido)-1-ethoxy-4-methylpentyl)thiazole-4-carboxamido)-2-methyl-5-phenylpentanoicacid (216): The TubOEt analogue at the Mep position was preparedaccording to the general procedure described above, employing racemic5,5-difluoro-1-methylpiperidine-2-carboxylic acid (224, prepared above)in Step 4, to provide 216 (3.05 mg) as a mixture of epimers. AnalyticalUPLC-MS (system 1): Epimer 1: t_(r)=2.06 min, m/z (ES+) calculated 750.4(M+H)⁺, found 750.3; Epimer 2: t_(r)=2.10 min, m/z (ES+) calculated750.4 (M+H)⁺, found 750.4.

(2S,4R)-4-(2-((1R,3R)-3-((2S,3S)—N,3-dimethyl-2-(2-methyl-2-azabicyclo[3.1.1]heptane-1-carboxamido)pentanamido)-1-ethoxy-4-methylpentyl)thiazole-4-carboxamido)-2-methyl-5-phenylpentanoicacid (217): The TubOEt analogue at the Mep position was preparedaccording to the general procedure described above, employing2-methyl-2-azabicyclo[3.1.1]heptane-1-carboxylic acid (225, preparedabove) in Step 4, to provide 217 (4.44 mg). Analytical UPLC-MS (system1): t_(r)=1.69 min, m/z (ES+) calculated 726.4 (M+H)⁺, found 726.3.

(2S,4R)-4-(2-((1R,3R)-3-((2S,3S)—N,3-dimethyl-24(1S,3R,4S)-2-methyl-2-azabicyclo[2.2.2]octane-3-carboxamido)pentanamido)-1-ethoxy-4-methyl-pentyl)thiazole-4-carboxamido)-2-methyl-5-phenylpentanoicacid (218): The TubOEt analogue at the Mep position was preparedaccording to the general procedure described above, employing(1S,3R,4S)-2-methyl-2-azabicyclo[2.2.2]octane-3-carboxylic (226,prepared above) acid in Step 4, to provide 218 (3.35 mg). AnalyticalUPLC-MS (system 1): t_(r)=1.74 min, m/z (ES+) calculated 740.4 (M+H)⁺,found 740.6.

(2S,4R)-4-(2-((1R,3R)-3-((2S,3S)—N,3-dimethyl-2-((1S,3R,4R)-2-methyl-2-azabicyclo[2.2.1]heptane-3-carboxamido)pentanamido)-1-ethoxy-4-methylpentyl)-thiazole-4-carboxamido)-2-methyl-5-phenylpentanoicacid (219): The TubOEt analogue at the Mep position was preparedaccording to the general procedure described above, employing(1S,3R,4R)-2-methyl-2-azabicyclo[2.2.1]heptane-3-carboxylic acid (227,prepared above) in Step 4, to provide 219 (2.82 mg). Analytical UPLC-MS(system 1): t_(r)=1.70 min, m/z (ES+) calculated 726.4 (M+H)⁺, found726.4.

(2S,4R)-4-(2-((3R,6S,9R,11R)-6-((S)-sec-butyl)-3,9-diisopropyl-2,8-dimethyl-4,7-dioxo-12-oxa-2,5,8-triazatetradecan-11-yl)thiazole-4-carboxamido)-2-methyl-5-phenylpentanoicacid (220): The TubOEt analogue at the Mep position was preparedaccording to the general procedure described above, employingN,N-dimethyl-D-valine in Step 4, to provide 220 (3.51 mg). AnalyticalUPLC-MS (system 1): t_(r)=1.72 min, m/z (ES+) calculated 716.4 (M+H)⁺,found 716.3.

(2S,4R)-4-(2-((1R,3R)-3-((2S,3S)-2-((R)-1,2-dimethylpyrrolidine-2-carboxamido)-N,3-dimethylpentanamido)-1-ethoxy-4-methylpentyl)thiazole-4-carboxamido)-2-methyl-5-phenylpentanoicacid (221): The TubOEt analogue at the Mep position was preparedaccording to the general procedure described above, employing(R)-1,2-dimethylpyrrolidine-2-carboxylic acid in Step 4, to provide 221(2.90 mg). Analytical UPLC-MS (system 1): t_(r)=1.67 min, m/z (ES+)calculated 714.4 (M+H)⁺, found 714.4.

In vitro assays. Cells cultured in log-phase growth were seeded for 24 hin 96-well plates containing 150 μL RPMI 1640 supplemented with 20% FBS.Serial dilutions of antibody-drug conjugates in cell culture media wereprepared at 4× working concentrations; 50 μL of each dilution was addedto the 96-well plates. Following addition of ADC, cells were incubatedwith test articles for 4 d at 37° C. After 96 h, growth inhibition wasassessed by CellTiter-Glo® (Promega, Madison, Wis.) and luminescence wasmeasured on a plate reader. The IC₅₀ value, determined in triplicate, isdefined here as the concentration that results in a 50% reduction incell growth relative to untreated controls.

In vivo xenograft models. All experiments were conducted in concordancewith the Animal Care and Use Committee in a facility fully accredited bythe Association for Assessment and Accreditation of Laboratory AnimalCare. Efficacy experiments were conducted in L540cy Hodgkin's lymphoma,Karpas:KarpasBVR anaplastic large cell lymphoma, MDR+ DELBVR anaplasticlarge cell lymphoma, and MDR+786-0 renal cell carcinoma xenograftmodels. Tumor cells were implanted sub-cutaneous in immune-compromisedSCID mice. Tumor cells, as a cell suspension, were implantedsub-cutaneous in immune-compromised SCID mice. Upon tumor engraftment,mice were randomized to study groups when the average tumor volumereached about 100 mm³. The ADC or controls were dosed once viaintraperitoneal injection. Tumor volume as a function of time wasdetermined using the formula (L×W²)/2. Animals were euthanized whentumor volumes reached 1000 mm³. Mice showing durable regressions wereterminated around day 100 post implant.

ADC Pharmacokinetic (PK) experiments. Pharmacokinetic (PK) experimentswere performed using radiolabeled antibody or ADC. PK test articles wereradiolabeled using the following procedure. To a solution of antibody orADC in PBS supplemented with an additional 50 mM potassium phosphate (pH8.0) and 50 mM sodium chloride was added 55 μCi N10 succinimidylpropionate, [propionate-2,3-3H]- (Moravek Biochemicals, Cat. No.: MT919, 80 Ci/mmol, 1 mCi/mL, 9:1 hexane:ethyl acetate solution) per mg ofantibody or ADC. The resulting mixture was vortexed and left at roomtemperature for 2 hours. The mixture was centrifuged at 4.000×g for 5minutes and the lower aqueous layer was removed and split into AmiconUltra-15 Centrifugal Filter Units (Millipore, Cat. No.: UFC903024, 30kDa MWCO). Unconjugated radioactivity was removed by 4 rounds ofdilution and centrifugation at 4,000×g. The resulting products werefiltered through sterile 0.22 μm Ultrafree-MC Centrifugal Filter Units(Millipore, Cat. No.: UFC30GV0S) and the final antibody or ADCconcentration was measured spectrophotometrically. The specific activity(μCi/mg) of each product was determined by liquid scintillationcounting.

The pharmacokinetic properties of the unconjugated antibody or ADC wereexamined in several rodent models. In each experiment, 1-3 mg ofradiolabeled antibody or ADC per kg of animal weight were injected viathe tail vein. Each test article was dosed once in replicate animals.Blood was drawn into K2EDTA tubes via the saphenous vein or by cardiacpuncture for terminal bleeds at various time points. Plasma was isolatedby centrifugation for 10 minutes at 10,000×g. A 10-20 μL of sample ofplasma from each time point was added to 4 mL Ecoscint-A liquidscintillation cocktail (National Diagnostics) and the totalradioactivity was measured by liquid scintillation 5 counting. Theresulting disintegrations per minute values were converted to μCi andthe specific activity of the radiolabeled test articles was used tocalculate the concentration of antibody or ADC remaining in the plasmaat each time point.

In vitro assays—tubulysin free drugs. Cells were treated for 96 hourswith tubulysin ether analogs (40-42) or tubulysin M (7), then assessedfor viability as described in the methods.

TABLE 1 Karpas299, L540cy, L428, HL60, HL60/RV, compd drug ALCL HL MDR +HL AML MDR + AML 7 TubM 0.17 0.14 0.11 0.3 2.2 40 TubOMe 0.19 0.12 0.50.13 29 41 TubOEt 0.05 0.05 0.14 0.05 5 42 TubOPr 0.15 0.13 0.4 0.17 14

The IC₅₀ values (nM) of Table 1 shows that all four test articles werehighly potent on each of the cell lines. The tubulysin ethyl ether (41)trended more potent than the methyl (40) and propyl (42) analogs. Theethyl ether and tubulysin M maintained the highest level of potency inthe context of MDR+L428 and HL60/RV cell lines.

TABLE 2 Karpas299, L540cy, L428, HL60, HL60/RV, compd drug ALCL HL MDR +HL AML MDR + AML 7 TubM 0.04 0.08 0.04 0.15 1 133 Tub-propionate 0.020.06 0.04 0.1 1 135 Tub-isobutyrate 0.02 0.1 0.12 0.1 6 134 Tub-butyrate0.011 0.04 0.05 0.08 3 136 Tub-isovalerate 0.02 0.06 0.11 0.04 6 137Tub-3,3-di- 0.18 0.7 0.93 0.7 47 Methylbutyrate 176 Tub-methyl- 0.120.06 0.12 0.07 6 (propen-2-yl) 177 Tub allyl ether 0.02 0.12 0.15 0.1 9178 Tub propargyl 0.05 0.17 0.41 0.2 27 ether 179 Tub benzyl ether 0.080.4 0.57 0.4 24

The tubulysin ester analogs (133-137) and unsaturated ether analogs(176-179) were tested in vitro for potency relative to tubulysin M (7),following a 96 hour exposure. As shown by IC50 values (nM) of Table 2,Tubulysin esters 133-136 performed comparably to tubulysin M, withsimilar potencies across of the cell lines. The most hindered, bulkytubulysin analog (137) displayed reduced potency relative to tubulysinM, with potency losses ranging from 5- to 47-fold relative to tubulysinM.

Tubulysin unsaturated ethers 176 and 177 displayed comparable potencycompared to the parent tubulysin 7. In contrast, the tubulysin propargyl(178) and benzyl (179) ethers were attenuated in potency relative totubulysin 7.

A series of analogues of the ethyl ether tubulysin compound TubOEt (41)were synthesized on solid phase lanterns that maintain the ethyl ethersubstitution, while either varying the residue at the Ile position(203-215) or the Mep position (216-221). Following cleavage from thesolid phase, the analogues were obtained in >85% purity and testedwithout further purification. The compounds were tested in vitro forpotency relative to a sample of TubOEt synthesized in parallel on alantern (41-lantern), following a 96 hour exposure, with IC₅O valuesexpressed in nM (Table 3). While in many cases an attenuation inactivity was observed relative to 41-lantern, some well-toleratedsubstitutions were found. At the Ile position the cyclic R⁵ substituentscyclopentyl (204) and cyclohexyl (205) afford potent compounds; however,the tetrahydropyranyl analogue (210) was inactive against all cell linestested. Furthermore, when Ile is replaced with allo-le (209) a loss of25- to 40-fold in potency is observed. While this stereochemicalpreference is not observed when Ile is replaced with O-methyl threonine(207) or O-methyl allothreonine (206), bulkier substituents led to agreater differentiation. Specifically, replacement with O-t-butylthreonine (215) provides an analogue significantly more potent than thecorresponding O-t-butyl allothreonine compound 216. Replacement of theMep residue was generally less-well tolerated. The most potent compoundsobtained in this series (217 and 221) possess substitution at the 4- and2-position of the piperidine or pyrrolidine-2-carboxylic acid core,respectively. Substitution at the 5-position (216) or 6-position (218and 219) led to a decrease in the observed cytotoxicity, particularly inthe HL60/RV cell line.

TABLE 3 Residue HepG2, L540cy, Ramos, U266 HL60, HL60/RV, compoundReplaced HCC HL NHL MM AML MDR + AML  41-lantern NA 2 0.3 0.3 0.3 4 94203 Ile 8 1 0.4 0.5 8 604 204 Ile 2 0.4 0.2 0.1 1 40 205 Ile 7 1 0.5 0.52 177 206 Ile 41 6 2 3 16 >1000 207 Ile 46 6 2 2 9 >1000 208 Ile 250 5844 40 221 >1000 209 Ile 50 12 7 8 15 >1000 210Ile >1000 >1000 >1000 >1000 >1000 >1000 211 Ile 14 2 1 2 5 224 212 Ile19 2 1 1 8 810 213 Ile 70 20 10 9 42 >1000 214 Ile 91 30 20 22 190 >1000215 Ile 1 0.2 0.2 0.1 1 33 216 Mep 58 12 10 9 61 >1000 217 Mep 2 1 0.40.4 4 244 218 Mep 9 5 6 7 24 >1000 219 Mep 19 6 8 8 25 >1000 220 Mep 4113 10 10 299 >1000 221 Mep 4 1 1 2 12 522

In vitro assays—tubulysin ADCs. ADCs were prepared by t Ell reduction ofinterchain disulfides to reveal 8-conjugatable cysteines/antibody thatwere alkylated through Michael addition with the maleimide-containingDrug Linker compounds. Anti-CD3 conjugates hearing quaternized tubulysinethers with and without a PEG12 side-chain were compared to theirtubulysin M analogs. Cells were treated with cAC10 (anti-CD30)Conjugates loaded at 8 drug/Ab for 96 h and then assessed for viability.The IC₅₀ values (ng/mL) are shown in Table 4.

TABLE 4 cAC10 ADCs DEL/BVR, DAR 8 Karpas299, L540cy, L428, DEL, MDR +drug-linker description ALCL HL MDR + HL ALCL ALCL 82 glucQ-TubM 0.6 40.5 2 3 56 glucQ-TubOMe 3 10 >1000 2 20 57 glucQ-TubOEt 1 5 4 2 5 58glucQ-TubOPr 2 6 117 2 10 99 PEG12-glucQ-TubM 0.3 2 0.5 1 2 66PEG12-glucO-TubOEt 1 5 6 2 6 67 PEG12-glucQ-TubOPr 4 10 >1000 2 12

The conjugate bearing the tubulysin ethyl ether linker 57 wasconsistently more potent than the methyl (56) or propyl (58) analogs.With the exception of L428, the tubulysin ethyl ether linker 57performed similarly to the tubulysin M analog 82. The presence of aPEG12 side chain in the linker had minimal impact on conjugate potency.All ADCs were inactive (no effect at 1000 ng/mL) on a CD30-negativeRamos NHL cell line, indicating a high degree of immunologicalspecificity.

TABLE 5 cAC10 DEL/B ADCs 8 MDPR- L428 VR, Hep3B drugs/mAb Linker-L540cy, MDR + DEL, MDR + CD30- drug-linker TubM HL HL ALCL ALCL HCC 15ValAlaPABQ 2 1 0.3 4 >1000 82 glucQ 1 0.4 0.3 4 >1000 91 ValGluPABQ 10.3 0.1 2 >1000 95 PEG12- 0.8 0.2 0.1 2 >1000 ValGluPABQ

Several hydrophilic linker constructs incorporating quaternizedtubulysin M were prepared and evaluated in vitro; the results are shownin Table 5. The data (IC₅₀ values in ng/mL) indicate that Conjugatesprepared from Drug Linker compounds having quaternized tubulysin Mlinked via a hydrophilic ValGlu dipeptide with (95) or without (91) aPEG12 side chain, or linked via a hydrophilic glucuronide (82) provideADCs that are equipotent to the ValAla comparator (15). All conjugatesdisplayed a high degree of immunological specificity, with IC₅₀s>1000ng/mL on antigen-negative Hep3B hepatocellular carcinoma cells.

In vivo xenograft models—comparison of dipeptide and glucuronide linkedtubulysin. Quaternary amine-linked tubulysin M conjugated with theValAla dipeptide linker (15) and glucuronide (82) were compared in aCD30+L540cy Hodgkin lymphoma xenograft model alongside theglucuronide-linked tubulysin ethyl ether (57). The glucuronidedrug-linker has been shown to offer improved physicochemical andpharmacokinetic conjugate properties relative to dipeptide linkers forADC payloads (Bioconjugate Chem., 2006, 17, 831-840; Nature Biotech,2014, 32, 1059-1062). Conjugates were loaded at 4-drugs/mAb to minimizethe effects of ADC PK. The results are shown in FIG. 1. Tumor-bearingmice were administered a single dose i.p. of test article once theaverage tumor volume reached 100 mm³ on day 7. Significantly greaterconjugate activity was observed when Tubulysin M (7) was conjugated inquaternized form as the glucuronide in cAC10-82. Mice treated with asingle dose of 0.6 mg/Kg cAC10-82 achieved 5/5 durable, completeregressions. In contrast, the cohort treated with one 0.6 mg/Kg dose ofthe ValAla dipeptide conjugate, cAC10-15, had one cure, with theremaining mice experiencing a transient tumor growth delay. A higherdose of 2 mg/Kg of the dipeptide conjugate was also inferior to theglucuronide, with only 2/5 mice cured at day 78. Thus, the glucuronidebased conjugate bearing tubulysin 7 was greater than 3-fold more potentthan the corresponding val-ala dipeptide control. Likewise, theglucuronide-linked tubulysin ethyl ether (41) in the form of conjugatecAC10-57 was also highly active. A single dose of 0.6 mg/Kg of cAC10-57induced 5/5 durable, complete regressions.

In vivo xenograft models—Effect of PEGylation with DAR 8 conjugates.Recently, we reported that addition of PEG side-chain to theglucuronide-monomethylauristatin E drug-linker provided improved ADCpharmacological properties with ADCs loaded at 8-drugs/mAb (NatureBiotech, 2014, 32, 1059-1062). A PEG12 side-chain was incorporated intoquaternary amine-linked tubulysin ethyl ether and propyl ether druglinker moieties providing Conjugates cAC10-66 and c-AC10-67,respectively. Anti-CD30 cAC10 conjugates loaded at 8-drugs/mAb wereprepared and evaluated relative to the non-PEGylated ethyl (cAC10-57)and propyl (cAC10-58) ether analogs in the L540cy xenograft model. Theresults are shown in FIG. 2. For ethyl and propyl ether glucuronideconstructs, inclusion of PEG12 resulted in enhanced antitumor activity.In the case of the ethyl ether, non-PEGylated Conjugate, cAC10-57induced a tumor growth delay in mice treated with a single dose of 0.5mg/Kg; whereas the PEGylated variant cAC10-66 provided cures in 5/5 miceat the same antibody dose. For the propyl ether, non-PEGylatedConjugate, cAC10-58 induced a tumor growth delay with outgrowth aroundday 40 in mice treated with a single dose of 0.5 mg/Kg; whereas thePEGylated variant cAC10-67 further delayed outgrowth to around day 60.

The PEGylated version of the glucuronide-tubulysin M, denoted as linker99, was also tested in the CD30+L540cy xenograft as a DAR 8 cAC10conjugate. As above, tumor-bearing mice were administered a single 0.5mg/Kg dose i.p. of test article once the average tumor volume reached100 mm³ on day 8. Like the PEGylated ethyl ether construct (cAC10-66)and the PEGylated Tubulysin M conjugate cAC10-99 induced 5/5 cures inmice treated at 0.5 mg/Kg.

A subset of antibody-drug conjugates were evaluated at lower doses inthe L540cy xenograft model. Anti-CD30 conjugates bearing PEGylated druglinker moieties containing quaternized tubulysin M (cAC10-99) orquaternized tubulysin ethyl ether (cAC10-66) were conjugated at8-drugs/mAb. Similarly, anti-CD30 conjugates bearing non-PEGylatedglucuronide drug linker moieties containing quaternized tubulysin M(cAC10-82) or quaternized tubulysin ethyl ether (cAC10-57), or theval-ala dipeptide version containing quaternized tubulysin M (cAC10-15)at 4-drugs/mAb were prepared. Mice bearing tumors were administered asingle dose of each Conjugate at 0.15 or 0.3 mg/kg once the tumorreached approximately 100 mm³. The results are shown in FIG. 8. At thelower dose of 0.15 mg/kg, all of the Conjugates displayed a tumor growthdelay, with the longest delay observed for mice treated with conjugate(cAC10-66) bearing PEGylated glucuronide drug linker moieties havingquaternized tubulysin ethyl ether quaternized Drug Units. At the 0.3mg/kg dose, durable, complete regressions were observed in 2/6 micetreated with ADC bearing non-PEGylated glucuronide drug linker moietieshaving quaternized tubulysin ethyl ether (cAC10-57) Drug Units and 3/6mice treated with conjugates bearing both PEGylated glucuronide druglinker moieties having quaternized tubulysin M (cAC10-99) or quaternizedtubulysin ethyl ether (cAC10-66) Drug Units.

In vivo xenograft models—demonstration of bystander effects. ThePEGylated constructs were tested in a Karpas:KarpasBVR xenograft modelof bystander activity. An equal number of CD30⁺ Karpas299 and CD30′KarpasBVR cells were injected subcutaneously to establish a tumor masswith a heterogeneous population of antigen positive and negative cells.Conjugates bearing warheads incapable of freely diffusing across plasmamembranes display minimal activity. Anti-CD30 cAC10 conjugates loaded at8-drugs/mAb with PEGylated glucuronide drug linker moieties bearingquaternized tubulysin M (cAC-10-99), quaternized tubulysin ethyl ether(cAC10-66), and quaternized tubulysin methyl-(propen-2yl) ether(cAC10-185) were evaluated. Tumor-bearing mice were administered asingle 0.5 mg/Kg dose i.p. of test article once the average tumor volumereached 100 mm³ on day 6. The results are shown in FIG. 4. All of themice treated with conjugates containing the quaternized tubulysin ether(cAC10-66 and cAC10-185) Drug Units achieved complete tumor regressionsthrough study day 41. The quaternized tubulysin M conjugate (cAC10-99)displayed more variable activity, with 2/5 mice achieving a completeregression at day 41 and the remaining 3/5 mice experiencing a transienttumor regression.

In vivo xenograft models—demonstration of activity in MDR+ models.Conjugates bearing the PEGylated constructs were tested in an MDR+786-0renal cell carcinoma and DELBVR anaplastic large cell lymphoma xenograftmodels. Anti-CD70 conjugates (mAb=h1F6) were loaded at 8-drugs/mAb withPEGylated glucuronide drug linker moieties containing quaternizedtubulysin M (cAC10-99), quaternized tubulysin ethyl ether (cAC10-66), orquaternized tubulysin methylpropene ether (cAC10-185) Drug Units. Micebearing CD70⁺ 786-0 renal cell carcinoma tumors were administered asingle dose of test articles at 0.5 or 1 mg/kg once the tumor reachedapproximately 100 mm³. The results are shown in FIG. 9. Tumor growthdelay was observed in mice treated with ADC conjugated to quaternizedtubulysin M (cAC10-99) at 0.5 mg/kg or with ADCs conjugated toquaternized tubulysin ethyl ether (cAC10-66) at 1.5 mg/kg. A higher doseof 1.5 mg/kg of the quaternized tubulysin M conjugate (cAC10-99) induced5/5 durable, complete regressions.

ADCs having a subset of the linkers were also tested in the MDR+,CD30-expressing DELBVR anaplastic large cell lymphoma xenograft model.Anti-CD30 conjugates (mAb=cAC10) bearing PEGylated linkers drug linkermoieties containing quaternized tubulysin M (cAC10-99) and quaternizedtubulysin ethyl ether (cAC10-66) were conjugated at 8-drugs/mAb.Similarly, anti-CD30 conjugates bearing non-PEGylated glucuronidedrug-linker moieties containing quaternized tubulysin M (cAC10-82) andquaternized tubulysin ethyl ether (cAC10-57), and the val-ala dipeptideversion of quaternized tubulysin M (cAC10-15) were conjugated at4-drugs/mAb. Mice bearing tumors were administered a single dose of testarticles at 0.3 or 1 mg/kg once the tumor reached approximately 100 mm³.The results are shown in FIG. 10. At the 0.3 mg/kg dose, Conjugateshaving PEGylated glucuronide drug linker moieties containing quaternizedtubulysin ethyl ether (cAC10-66) provided 2/5 durable, completeregressions and having PEGylated glucuronide drug linker moietiescontaining quaternized tubulysin M (cAC10-99) provided 5/5 durable,complete regressions. At the higher dose of 1 mg/kg, durable, completeregressions were observed with the non-PEGylated glucuronide tubulysinethyl ether (1/5, cAC10-57) and tubulysin M (5/5 mice cured, cAC10-82)Conjugates. In the PEGylated series, a dose of 1 mg/kg provided 4/5 and5/5 durable, complete regressions for the glucuronide tubulysin ethylether (cAC10-66) and tubulysin M (cAC10-99) Conjugates, respectively.

Rat pharmacokinetic assessment. FIGS. 5-7 contain the clearance profilesfor various tubulysin quaternary amine linker constructs. In allexperiments, rats were administered a single i.v. dose at 1 mg/Kg attime zero with radiolabeled ADCs. Plasma samples were collected atvarious time points and analyzed as described to quantify total antibodyas a function of time. FIG. 5 contains the exposure profiles forhumanized IgG conjugates prepared from the Drug Linker compoundMDPR-val-ala-PABQ-TubM (15) and the hydrophilic Drug Linker compoundsMDPR-GlucQ-TubM (82) MDPR-val-glu-TubM (91), andMDPR-val-glu(PEG12)-TubM (9). Humanized IgG bearing four copies of theval-Ala dipeptide-linked quaternized TubM (hIgG 15) had a clearanceprofile identical to unmodified antibody; however, at a DAR of 8 the ADCwas cleared from circulation much more rapidly. Substitution of thealanine residue of hIgG-15 with the glutamate residue providing IgG-91did not result in an appreciable increase in exposure. Addition of aPEG12 side chain to the val-glu linker of hIgG-91, resulting in hIgG-95,did provide an increase in ADC exposure. Likewise, replacement of theval-ala dipeptide of IgG-15 with a Glucuronide Unit providing hIgG-82did result in an increase in conjugate exposure with DAR 8 conjugates.

FIG. 6 contains the PK exposures for DAR 8 humanized IgG conjugatesbearing the glucuronide quaternary amine-linked tubulysin propyl etherdrug linker moieties in the absence (hIgG-58) and presence (hIgG-67) ofa PEG12 side chain. The conjugate bearing 8 copies of quaternized druglinker moieties from the Drug linker compound MDPR-glucQ-TubOPr (58) wascleared from circulation much more rapidly than the unmodified antibody.The addition of a PEG12 side chain providing hIgG-67 significantlyimproved exposure, more closely approximating naked antibody PKproperties.

The PK exposure of DAR 8 humanized IgG conjugates containing PEGylatedglucuronide drug linkers moieties having quaternized tubulysin M(hIgG-99) and quaternized tubulysin ethyl ether (hIgG-66) Drug Units areshown in FIG. 7. Both conjugates displayed prolonged exposures closelyapproximating a line representing the historical mean exposure for theparental antibody.

1-34. (canceled)
 35. A Drug-Linker compound, wherein the compound hasthe structure of Formula IA:

or a salt thereof, wherein L_(B)′ is a Ligand Covalent Binding Unitprecursor; L_(P) is a Parallel Connector Unit; PEG is a PolyethyleneGlycol Unit; subscript a is 0 or 1; subscript b is 0 or 1; A is a firstoptional Stretcher Unit so that subscript a is 0 when A is absent or Ais present so that subscript a is 1 and optionally comprises two, threeor four independently selected subunits (A₁, A₂, A₃, A₄); B is aBranching Unit or a second optional Stretcher Unit (A_(O)) so thatsubscript b is 0 when B is absent or B is present so that subscript b is1 and optionally comprises two, three or four subunits independently ofA; subscript n is 1, 2, 3 or 4, provided that subscript b is 1 and B isa Branching Unit when subscript n is 2, 3 or 4 and provided that B isA_(O) or is absent when subscript n is 1; Su is a carbohydrate moiety;—O′— represents an oxygen atom of an O-glycosidic bond cleavable by aglycosidase; -J′- represents a heteroatom, optionally substituted whennitrogen, from a functional group of B, when B is present, or of L_(P),when B is absent; V, Z¹, Z² and Z³ are ═N— or ═C(R²⁴)—, wherein R²⁴ ishydrogen or alkyl, alkenyl or alkynyl, optionally substituted, orhalogen, —NO₂, —CN or other electron withdrawing group, an electrondonating group, —O′-Su, or —C(R⁸)(R⁹)-D⁺, wherein at least at least twoof V, Z¹, Z² and Z³ are ═C(R²⁴)—, wherein one R²⁴ is —C(R⁸)(R⁹)-D andone other R²⁴ is —O′-Su, wherein the —O′-Su and —C(R⁸)(R⁹)-D⁺substituents are ortho or para to each other; R⁸ and R⁹ independentlyare hydrogen or optionally substituted alkyl, alkenyl alkynyl, aryl, orheteroaryl; R′ is hydrogen or is halogen, —NO₂, —CN or other electronwithdrawing group; D⁺ is a quaternized tubulysin Drug Unit preferablyhaving the structure of:

wherein the circle represents an 5-membered nitrogen-containingheteroarylene and wherein the indicated required substituents to thatheteroarylene are in a 1,3-relationship with each other with optionalsubstitution at the remaining positions; subscript m is 0 or 1; R^(2A)is hydrogen or optionally substituted alkyl or R^(2A) along with theoxygen atom to which it is attached defines an O-linked substituentother than —OH; R³ is hydrogen or optionally substituted alkyl; R⁴, R⁵and R⁶ are optionally substituted alkyl; one R⁷ is an optionallysubstituted alkyl, an optionally substituted arylalkyl, optionallysubstituted heteroarylalkyl and the other R⁷ is hydrogen or anoptionally substituted alkyl; and R^(8A) is hydrogen or optionallysubstituted alkyl, wherein the wavy line indicates covalent bonding ofD⁺ to the remainder of the Drug-Linker compound structure and whereinoptionally substituted alkyl are independently selected; and whereinsaid glycosidase cleavage results in release of tubulysin compound (D)from the Drug-Linker compound or a Ligand Drug Conjugate compoundprepared from the Drug-Linker compound.
 36. The Drug-Linker compound ofclaim 35, wherein L_(B)′- has a structure selected from the groupconsisting of:

wherein R is hydrogen or C₁-C₆ optionally substituted alkyl; R″ ishydrogen or halogen or R and R′ are independently selected halogen; T is—Cl, —Br, —I, —O-mesyl or —O-tosyl or other sulfonate leaving group; Uis —F, —Cl, —Br, —I, —O—N-succinimide, —O-(4-nitrophenyl),—O-pentafluorophenyl, —O-tetrafluorophenyl or —O—C(═O)—OR⁵⁷; and X² isC₁₋₁₀ alkylene, C₃-C₈-carbocycle, —O—(C₁-C₆ alkyl), -arylene-, C₁-C₁₀alkylene-arylene, -arylene-C₁-C₁₀ alkylene, —C₁-C₁₀alkylene-(C₃-C₆-carbocycle)-, —(C₃-C₈ carbocycle)-C₁-C₁₀ alkylene-,C₃-C₈-heterocycle, —C₁-C₁₀ alkylene-(C₃-C₈ heterocyclo)-,—C₃-C₈-heterocyclo)-C₁-C₁₀ alkylene, —(CH₂CH₂O)_(u), or—CH₂CH₂O)_(u)—CH₂—, wherein subscript u is an integer ranging from 1 to10 and R⁵⁷ is C₁-C₆ alkyl or aryl.
 37. The Drug-Linker compound of claim35, wherein the compound has the structure of one of Formula IIA-IIF:

or a salt of any of the foregoing.
 38. The Drug-Linker compound of claim37, wherein —O′-Su has the structure of Formula 3:

wherein the wavy line represents covalent bonding of O′ to the remainderof the Drug-Linker compound structure; and R⁴⁵ is —CH₂OH or —CO₂H. 39.The Drug-Linker compound of claim 35, wherein the compound has thestructure of Formula IV:

or a salt thereof, wherein J′ is —N(R³³)—, wherein R³³ is hydrogen ormethyl; V and Z³ independently are ═CH— or ═N—; R′ is hydrogen or anelectron withdrawing group; R⁸ is hydrogen; R⁹ is hydrogen, optionallysubstituted C₁-C₆ alkyl or optionally substituted phenyl; and R⁴⁵ is—CO₂H.
 40. The Drug-Linker compound of claim 35, or a salt thereof,wherein subscript a is 1; and L_(B)′-A- of Formula IA has the structureof Formula V:

wherein the —[C(R^(b1))(R^(b1))]_(q)—[HE]- moiety is A or A₁, wherein A₁is a subunit of A; A₂₋₄ are optional subunits of A; R is hydrogen,chloro or C₁-C₄ alkyl; R″ is hydrogen or chloro; R^(a1) is hydrogen,optionally substituted alkyl or a Basic Unit (BU), optionally protected;R^(a2) is hydrogen or optionally substituted alkyl, or R^(a1) and R^(a2)together with the carbon atom to which they are attached define anitrogen-containing heterocycloalkyl; HE is an optional HydrolysisEnhancer (HE) Unit; subscript q is an integer ranging from 0 to 6; eachR^(b1) independently is hydrogen, optionally substituted C₁-C₆ alkyl,optionally substituted aryl or optionally substituted heteroaryl, or twoR^(b1) together with the carbon(s) to which they are attached define aC₃-C₆ cycloalkyl or one R^(b1) and HE together with the carbon to whichthey are attached define a 5 or 6-membered cycloalkyl or a 5- or6-membered heterocycloalkyl and the other R^(b1) is hydrogen, optionallysubstituted C₁-C₆ alkyl, optionally substituted aryl or optionallysubstituted heteroaryl; BU, optionally protected, has the structure of—[C(R¹)(R¹)]—[C(R²)(R²)]r-N(R²²)(R²³), or an acid addition salt thereof,wherein subscript r is 0, 1, 2 or 3; each R¹ independently is hydrogenor C₁-C₄ alkyl or two R¹ together with the carbon to which they areattached comprise a C₃-C₆ cycloalkyl, and each R² independently ishydrogen, optionally substituted C₁-C₆ alkyl, optionally substitutedaryl or optionally substituted heteroaryl, or two R² together with thecarbon(s) to which they are attached and any intervening carbons definea C₃-C₆ cycloalkyl, or one R¹ and one R² together with the carbons towhich they are attached and any intervening carbons define a 5- or6-membered cycloalkyl and the remaining R¹ and R² are as defined; andR²² and R²³ independently, hydrogen, optionally substituted C₁-C₆ alkyl,or an acid-labile protecting group, or together with the nitrogen towhich they are attached define a 5- or 6-membered heterocycloalkyl, orone of R²², R²³ is hydrogen and the other is an acid labile protectinggroup; and wherein the wavy line indicates the site of covalentattachment to the remainder of the Drug-Linker compound structure. 41.The Drug-Linker compound of claim 40, or a salt thereof, wherein FormulaV has the structure of Formula VA:

wherein subscript q is an integer ranging from 0 to
 4. 42. TheDrug-Linker compound of claim 40, or a salt thereof, wherein Formula Vhas the structure of Formula VB:

wherein one of R²², R²³ is hydrogen and the other is an acid labilecarbamate protecting group; and subscript q is an integer ranging from 0to
 4. 43. The Drug-Linker compound of claim 41, or a salt thereof,wherein Formula VA or Formula VB has the structure of:

respectively.
 44. The Drug-Linker compound of claim 40, wherein thecompound has the structure of Formula VI:

or a salt thereof, wherein the asterisk (*) designates chirality orabsence thereof at the indicated carbon; A₂₋₄ are independently selectedoptional subunits of A, wherein —[C(R^(b1))(R^(b1))]_(q)—[HE]- is A₁when one or more such subunits are present; one of R and R″ is hydrogenand the other is hydrogen or chloro; R′ is hydrogen or an electronwithdrawing group; R^(a1) is hydrogen or a basic unit (BU), optionallyprotected, having the structure of —CH₂—N(R²²)(R²³), or an acid additionsalt thereof, wherein R²² and R²³ independently are hydrogen, methyl orethyl or both together with the nitrogen atom to which they are attacheddefine a 5- or 6-membered heterocycloalkyl, or one of R²², R²³ ishydrogen and the other is an acid labile carbamate protecting group;R^(a2) is hydrogen; subscript q is an integer ranging from 0 to 5 whenHE is present or from 1 to 5 when HE is absent; each R^(b1)independently is hydrogen or optionally substituted C₁-C₆ alkyl; HE isabsent or is —C(═O)—; R⁴⁵ is —CO₂H; J′ is —NH—; V and Z³ are each ═CH—;R⁸ is hydrogen; and R⁹ is hydrogen or methyl.
 45. The Drug-Linkercompound of claim 44, or a salt thereof, wherein the indicated starred(*) carbon is predominantly in the same absolute configuration as thealpha carbon of an L-amino acid when that indicated carbon is chiral.46. The Drug-Linker compound of any one of claim 35, or a salt thereof,wherein A and A_(O) independently have the structure of Formula 7 orFormula 8:

wherein the wavy lines indicated covalent attachment within theremainder of the Drug-Linker compound structure, wherein K and Lindependently are C, N, O or S, provided that when K or L is O or S, R⁴¹and R⁴² to K or R⁴³ and R⁴⁴ to L are absent, and when K or L are N, oneof R⁴¹, R⁴² to K or one of R⁴², R⁴³ to L are absent, and provided thatno two adjacent L are independently selected as N, O, or S; whereinsubscripts e and f are independently selected integers that range from 0to 12, and subscript g is an integer ranging from 1 to 12; wherein G ishydrogen, optionally substituted C₁-C₆ alkyl, —OH, —OR^(PR), —CO₂H,CO₂R^(PR), wherein R^(PR) is a suitable protecting, —N(R^(PR))(R^(PR)),wherein R^(PR) are independently a protecting group or R^(PR) togetherform a suitable protecting group, or —N(R⁴⁵)(R⁴⁶), wherein one of R⁴⁵,R⁴⁶ is hydrogen or R^(PR), wherein R^(PR) is a suitable protectinggroup, and the other is hydrogen or optionally substituted C₁-C₆ alkyl;wherein R³⁸ is hydrogen or optionally substituted C₁-C₆ alkyl; R³⁹—R⁴⁴independently are hydrogen, optionally substituted C₁-C₆ alkyl,optionally substituted aryl, or optionally substituted heteroaryl, orboth R³⁹, R⁴⁰ together with the carbon to which they are attachedcomprise a C₃-C₆ cycloalkyl, or R⁴¹, R⁴² together with K to which theyare attached when K is C, or R⁴³, R⁴⁴ together with L to which they areattached when L is a carbon atom comprise a C₃-C₆ cycloalkyl, or R⁴⁰ andR⁴¹, or R⁴⁰ and R⁴³, or R⁴¹ and R⁴³ to together with the carbon atom orheteroatom to which they are attached and the atoms intervening betweenthose carbon atoms and/or heteroatoms comprise a 5- or 6-memberedcycloalkyl or heterocycloalkyl, provided that when K is O or S, R⁴¹ andR⁴² are absent, when K is N, one of R⁴¹, R⁴² is absent, when L is O orS, R⁴³ and R⁴⁴ are absent, and when L is N, one of R⁴³, R⁴⁴ is absent,or wherein A_(O) is an alpha-amino, beta-amino or anotheramine-containing acid residue.
 47. The Drug-Linker compound of any oneof claim 35, or a salt thereof, wherein the quaternized tubulysin DrugUnit (-D⁺) has the structure of:

wherein subscript m is 0 or 1; Z is an optionally substituted alkyleneor an optionally substituted alkenylene; and R^(7A) is optionallysubstituted aryl or optionally substituted heteroaryl.
 48. TheDrug-Linker compound of claim 47, or a salt thereof, wherein thequaternized tubulysin Drug Unit (-D⁺) has the structure of:

wherein R^(7A) is optionally substituted phenyl and R⁸ is hydrogen ormethyl.
 49. The Drug-Linker compound of claim 48, or a salt thereof,wherein the quaternized tubulysin Drug Unit (-D⁺) has the structure of:

wherein R⁴ is methyl; subscript u is 0, 1 or 2; R³ is H, methyl, ethyl,propyl, —CH₂—OC(O)R^(3A), —CH₂CH(R^(3B))C(O)R^(3A) or—CH(R^(3B))C(O)NHR^(3A), wherein R^(3A) is C₁-C₆ alkyl and R^(3B) is Hor C₁-C₆ alkyl, independently selected from R^(3A); R^(2A) along withthe oxygen atom to which it is attached is an O-linked substituentselected from the group consisting of —OCH₂OCH₂R^(2B), —OCH₂R^(2B),—OC(O)R^(2B), —CH₂OC(O)R^(2B), —OC(O)N(R^(2B))(R^(2C)), and—OCH₂C(O)N(R^(2B))(R^(2C)), wherein R^(2B) and R^(2C) are independentlyselected from the group consisting of H, C₁-C₆ alkyl and C₂-C₆ alkenyl;and each R^(7B), when present, independently is —OH or —OCH₃.
 50. TheDrug-Linker compound of claim 49, or a salt thereof, wherein thequaternized tubulysin Drug Unit (-D⁺) has the structure of:


51. The Drug-Linker compound of claim 50, or a salt thereof, whereinR^(2A) is —CH₂CH₃.
 52. The Drug-Linker compound of claim 50, or a saltthereof, wherein R^(2A) is —CH₂—CH═CH₂.
 53. The Drug-Linker compound ofclaim 49, or a salt thereof, wherein R^(2A) is —CH₂CH₃, —CH₂—CH═CH₂ or—CH₂C(CH₃)═CH₂, R^(2B) is —CH₃, R³ is —CH₃ and subscript u is 0, orR^(2A) is —CH₂CH₃ or —CH₂—CH═CH₂, or —CH₂C(CH₃)═CH₂, R^(2B) is —CH₃, R³is —CH₃ and subscript u is 1, wherein R^(7B) is —OH.
 54. The Drug-Linkercompound of claim 49, or a salt thereof, wherein the quaternizedtubulysin Drug Unit (-D⁺) has the structure of:

wherein R^(2B) is —CH₃, —CH₂CH₃, —CH₂CH₂CH₃, —CH(CH₃)₂, —CH₂CH(CH₃)₂, or—CH₂C(CH₃)₃.
 55. Drug-Linker compound of claim 49, or a salt thereof,wherein the quaternized tubulysin Drug Unit (-D⁺) has the structure of:

wherein R^(2B) is hydrogen, methyl or —OCH₃, or —OCH₂R^(2B) is—OCH₂CH═CH₂ or —OCH₂C(CH₃)═CH₂.
 56. The Drug-Linker compound of claim49, or a salt thereof, wherein the quaternized tubulysin Drug Unit -D⁺is that of tubulysin M, for which the structure is:


57. The Drug-Linker compound of any one of claim 35, or a salt thereof,wherein L_(P) is a aminoalkanedioic acid, a diaminoalkanoic acid, asulfur-substituted alkanedioic acid, a sulfur-substituted aminoalkanoicacid, a diaminoalkanol, an aminoalkanediol, a hydroxyl substitutedalkanedioic acid, a hydroxyl substituted aminoalkanoic acid or asulfur-substituted aminoalkanol residue, optionally substituted, whereinthe sulfur substituent is in reduced or oxidized form, or L_(P) is anamino acid residue of lysine, arginine, asparagine, glutamine,ornithine, citrulline, cysteine, homocysteine, penicillamine, threonine,serine, glutamic acid, aspartic acid, tyrosine, histidine or tryptophan,wherein the amino acid is in the D- or L-configuration.
 58. TheDrug-Linker compound of claim 57, or a salt thereof, wherein theaminoalkanedioic acid, diaminoalkanoic acid, sulfur-substitutedaminoalkanoic acid or hydroxyl substituted aminoalkanoic acid residuehas the structure of Formula A or Formula B:

wherein subscript v is an integer ranging from 1 to 4; subscript v′ isan integer ranging from 0 to 4; X^(LP) is selected from the groupconsisting of —O—, —NR^(LP)—, —S—, —S(O)—, —S(═O)₂—, —C(═O)—,—C(═O)N(R^(LP))—, —N(R^(LP))C(═O)N(R^(LP))—, and—N(R^(LP))C(═NR^(LP))N(R^(LP))— wherein each R^(LP) is independentlyselected from the group consisting of hydrogen and optionallysubstituted alkyl or two of R^(LP) together along with their interveningatoms define an optionally substituted heterocycloalkyl and anyremaining R^(LP) are as previously defined; Ar is an arylene orheteroarylene, optionally substituted; each R^(E) and R^(F) isindependently selected from the group consisting of —H, optionallysubstituted alkyl, optionally substituted aryl and optionallysubstituted heteroaryl, or R^(E) and R^(F) together with the same carbonto which they are attached, or R^(E) and R^(F) from adjacent carbonstogether with these carbons, defines a optionally substituted cycloalkylwith any remaining R^(E) and R^(F) substituents as previously defined;and wherein the wavy lines indicates covalent attachment of the FormulaA or Formula B structure within the Drug-Linker structure.
 59. TheDrug-Linker compound of any one of claim 35, or a salt thereof, wherein-L_(P)(PEG)- has the structure of Formula A1 or A2:

wherein X^(LP) is selected from the group consisting of —O—, —NH, —S—and —C(═O)—; R^(E) and R^(F) are independently selected from the groupconsisting of —H, and —C₁-C₄ alkyl; and wherein the wavy line indicatescovalent attachment of Formula A1 or Formula A2 within the Drug-Linkercompound structure.
 60. The Drug-Linker compound of claim 35, whereinthe compound is represented by the structure of:

or a salt thereof, wherein R^(2A) is saturated C₁-C₄ alkyl, unsaturatedC₂-C₄ alkyl, —C(═O)R^(2B), wherein R^(2B) is C₁-C₄ alkyl; A_(O) isabsent or is an amine-containing acid residue; subscript q is an integerranging from 1 to 4; subscript u is 0 or 1; subscript v is an integerranging from 1 to 4; R^(7B), when present, is —OH; X^(LP) is selectedfrom the group consisting of —O—, —NH, —S— and —C(═O)—; R^(E) and R^(F)are independently selected from the group consisting of —H, and C₁-C₄alkyl; one of R²², R²³ is hydrogen and the other is an acid labileprotecting group or R²² and R²³ are each hydrogen with the nitrogen towhich they are attached optionally protonated as an acid addition salt.61. The Drug-Linker compound of claim 60, or a salt thereof, whereinR^(2A) is saturated C₁-C₄ alkyl or unsaturated C₃-C₄ alkyl, whereinsaturated C₁-C₄ alkyl is —CH₃, —CH₂CH₃, —CH₂CH₂CH₃ and unsaturated C₃-C₄alkyl is —CH₂CH═CH₂ or —CH(CH₃)CH═CH₂.
 62. The Drug-Linker compound ofclaim 60, or a salt thereof, wherein R^(2A) is —C(O)CH₃.
 63. TheDrug-Linker compound of claim 60, or a salt thereof, wherein R^(2A) is—CH₂CH₃.
 64. The Drug-Linker compound of claim 60, or a salt thereof,wherein R^(2A) is —CH₂CH═CH₂.
 65. The Drug-Linker compound of claim 35,or a salt thereof, wherein PEG has the structure selected from the groupconsisting of:

wherein the wavy line indicates site of attachment to X^(LP) of theParallel Connector Unit (L_(P)), R^(PEG1) is an optional PEG AttachmentUnit, R^(PEG2) is a PEG Capping Unit; R^(PEG3) is an PEG Coupling Unit;subscript n ranges from 2 to 72; each subscript n′ is independentlyselected from 1 to 72; and subscript e ranges from 2 to
 5. 66. TheDrug-Linker compound of claim 60, or a salt thereof, wherein —X^(LP)—PEGhas the structure of:


67. The Drug-Linker compound of claim 66, or a salt thereof, whereinsubscript n is 12 and R^(PEG2) is hydrogen or —CH₃.
 68. The Drug-Linkercompound of claim 60, or a salt thereof, wherein the compound has thestructure of:

wherein subscript u is 0 or 1; R^(7B), when present, is —OH; and R^(2A)along with the oxygen atom to which it is attached is —OC(O)CH₃, —CH₂CH₃or —CH₂CH═CH₂.
 69. The Drug-Linker compound of claim 68, or a saltthereof, wherein the compound has the structure of:

70-101. (canceled)